[#523] Edit the extensions docs

Just a couple of small edits

doc/extensions.rst

@@ -41,7 +41,9 @@ Writing Extensions
 
 .. note::
 
-    An `extension` defines one or more `plugins`.  Each of this plugins implements one or more `plugin interfaces`.
+    A CKAN **extension** is a Python package that contains one or more
+    **plugins**. A plugin is a class that implements one or more of CKAN's
+    **plugin interfaces**.
 
 
 Plugins: An Overview

doc/overview.rst

@@ -0,0 +1,185 @@
+========
+Overview
+========
+
+.. Intro para
+    - Remember you're not selling CKAN this is for sysadmins
+    - What is CKAN?
+    - What does it have and what makes it ideal for what?
+    - Who is CKAN "aimed at"
+    - Who is it developed by
+    - Open source
+    - What is this page?
+    - Link to ckan.org
+
+    the world’s leading open-source data portal platform 
+
+    the open source data portal software
+
+    CKAN is a powerful data management system that makes data **accessible** – by
+    providing tools to streamline **publishing**, sharing, **finding** and **using** data. CKAN
+    is aimed at data publishers (national and regional governments, companies and
+    organizations) wanting to make their data open and available.
+
+    Used to power both official and community data portals, CKAN was developed by
+    the non-profit Open Knowledge Foundation to run the Datahub.io. It now powers
+    more than 40 data hubs around the world, including portals for local, national
+    and international government, such as the UK’s data.gov.uk and the European
+    Union’s publicdata.eu.
+
+    * * *
+
+Welcome to CKAN's documentation. This section will give an overview of CKAN,
+including it's major features and key concepts.
+
+
+--------------------
+Datasets & Resources
+--------------------
+
+Data in CKAN is published as datasets, which contain resources. A CKAN
+**resource** is a data file (such as a CSV or Excel file) that is either linked
+to from CKAN or uploaded to CKAN, or a link to a data API, plus some associated
+metadata (name, description, etc). A **dataset** is a collection of one or more
+resources, plus some associated metadata (title, description, license, etc).
+Datasets and resources can be added to CKAN using the web interface, or over
+the API.
+
+
+-------------
+Web Interface
+-------------
+
+.. Publishing data: web interface, API, harvester.
+With CKAN's web interface, users can easily add and edit datasets and
+resources.
+
+
+---------
+FileStore
+---------
+
+If a data file has already been published on another site, a user can enter a
+link to the file into a CKAN resource. If they would like to publish the file
+using CKAN, CKAN's FileStore adds an *Upload* button and can upload files to
+the CKAN server itself or to cloud storage such as Amazon S3 or Google Cloud
+Storage.
+
+
+---------
+DataStore
+---------
+
+Whether a resource file has been linked-to from CKAN or uploaded to CKAN, the
+data contained within the file can be pulled into CKAN's DataStore. The
+DataStore is a database for structured storage of data, that provides an API
+for applications to search and update the data without having to download the
+entire data file. CKAN's data previewer uses the DataStore API to provide
+table, graph and map visualisations of data.
+
+.. todo:: How does data get into the datastore?
+
+
+------
+Search
+------
+
+CKAN's **search** interface lets you search for datasets using quick
+‘Google-style’ key word searches. You can filter search results according to
+the datasets' organizations, groups, tags, file formats, or licenses, and sort
+search results by relevance, modification time, or name.
+
+.. _solr: http://lucene.apache.org/solr/
+
+
+----------------------------
+Activity Streams & Following
+----------------------------
+
+As datasets, groups and organizations are added and updated, CKAN logs each
+activity in an activity stream. You can follow a users, datasets, groups and
+organizations and get notified on your CKAN dashboard or (optionally) by email
+when they have new activity.
+
+.. todo:
+
+   The history pages/revisions aren't mentioned here, because they aren't
+   exposed in the web interface in 2.0. Once we decide what to do with the
+   history pages (put them back in? or merged them with activity streams?)
+   we can update these.
+
+
+-------------------------------
+Data Preview and Visualisations
+-------------------------------
+
+CKAN's built-in data viewer displays previews and visualisations of data from
+CKAN resources, including:
+
+Table view: If structured data is uploaded or linked to CKAN as a .csv or Excel table, the DataStore loads it into a database, allowing CKAN to give a range of ways to view and process the data. Initially it is displayed as a table. The user can sort the data on particular columns, filter or facet by values, or hide columns entirely.
+
+Graphing data: You can also display the data on a graph, choosing the variables on the axes and comparing a number of variables by graphing them together on the same y-axis.
+
+Mapping data: If the table has columns that CKAN recognises as latitude and longitude, it can plot the data points on a map, which can be panned (dragged) and zoomed. Selecting a data point displays all the field values in the corresponding row.
+
+Image data: CKAN’s previewing is not restricted to tabular data. Common image formats will be displayed, and if a resource is a web page, it will also be previewed directly in the CKAN dataset.
+
+Roll your own: CKAN’s built-in previews use the DataStore’s API. If you have your own data previewing tools or are planning to build them, it’s easy to plug them into the API so that you can create visualisations on the fly, without the need for users to download the data. 
+
+
+---------------
+Tags and Groups
+---------------
+
+Datasets in CKAN can be sorted into tags and groups. **Tags** are free-form way
+to sort datasets, anyone who can edit a dataset can add any tag to that
+dataset, and can create new tags. **Groups** are more controlled, only group
+members can add datasets to a group, and group admins add new members to
+groups.
+
+.. todo:: Tag vocabularies?
+
+
+-----------------------------
+Organizations & Authorization
+-----------------------------
+
+**Organizations** are the primary way of controlling access to datasets in
+CKAN. Organization admins add users to organizations, and only members of
+organizations can add datasets to the organization or update the organization's
+datasets. **Private datasets** can only be seen by members of the datasets'
+organizations. When they're ready to publish, organization admins make datasets
+public. As with tags and groups, users can browse and search datasets by
+organization.
+
+
+-------------
+Configuration
+-------------
+
+CKAN sysadmins can configure CKAN using a simple web interface. More advanced
+configuration options can be set in CKAN's configuration file.
+
+-------
+Theming
+-------
+
+If you're comfortable with HTML and CSS, you can create your own custom CKAN
+theme. CKAN themes have complete freedom to modify and override all the
+templates, so you can make it look however you want.
+
+
+----------
+Extensions
+----------
+
+
+---
+API
+---
+
+-----------------------------------------
+Command-Line Interface for Administrators
+-----------------------------------------
+
+For sysadmins, CKAN provides a command-line interface

doc/toolkit.rst

@@ -4,7 +4,7 @@ Plugins Toolkit
 
 To allow a safe way for extensions to interact with ckan a toolkit is
 provided. We aim to keep this toolkit stable across ckan versions so
-that extensions will work across diferent versions of ckan.
+that extensions will work across different versions of ckan.
 
 .. Note::