added database scheme to documentation

docs/migration.rst

@@ -0,0 +1,42 @@
+Migration
+=========
+
+Migrating from 1.X.X to 2.0.0
+-----------------------------
+Version 2.0.0 offers a lot more functionality, including Request- and Endpoint-profiling.
+
+There are two migrations that you have to do, before you can use version 2.0.0.
+
+1. **Migrate the database:** Since version 2.0.0 has a different database scheme, the 
+   Flask-MonitoringDashboard cannot automatically migrate to this version.
+
+   We have created a script for you that can achieve this. It migrates the data in the existing 
+   database into a new database, without removing the existing database.
+
+   If you want to run this script, you need to be aware of the following:
+
+   - If you already have version 1.X.X of the Flask-MonitoringDashboard installed, first update to 
+     2.0.0 before running this script. You can update a package by:
+
+     .. code-block:: bash
+ 
+        pip install flask_monitoringdashboard --upgrade
+
+   - set **OLD_DB_URL** on line 16, such that it points to your existing database.
+
+   - set **NEW_DB_URL** on line 17, to a new database name version. Note that they can't be the same.
+
+   - Once you have migrated your database, you have to update the database location in your configuration-file.
+
+   - You can find `the migration script here`_.
+
+     .. _`the migration script here`: https://github.com/flask-dashboard/Flask-MonitoringDashboard/tree/master/flask_monitoringdashboard/migrate_v1_to_v2.py
+
+2. **Migrate the configuration file**: You also have to update the configuration file completely, since we've 
+   re factored this to make it more clear. The main difference is that several properties have been re factored
+   to a new header-name. 
+
+   For an example of a new configuration file, see `this configuration file`_.
+
+   .. _`this configuration file`: https://github.com/flask-dashboard/Flask-MonitoringDashboard/tree/master/config.cfg
+