Schemas and schema-based validation (#155)

* added schemas for some edge and node types as well as circuit config
* Rework the circuit validation
* Removed non-BBP related checks
* Removed checking for missing fields (handled by schemas.py)
* Continue the checks as far as possible even if errors show up
* added skip-slow option (with default true) to the validate command
* Removed redundant test cases, combined some of them
* Added tests for schemas
* use unittest.mock instead of mock
* updated CHANGELOG

Co-authored-by: Joni Herttuainen <joni.herttuainen@epfl.ch>

CHANGELOG.rst

@@ -4,15 +4,23 @@ Changelog
 Version v1.0.0
 ---------------
 
+New Features
+~~~~~~~~~~~~
+- jsonschema based validation of h5 files and circuit configuration
+  - checks for required attributes and data types of attributes (in h5 files)
+
 Improvements
 ~~~~~~~~~~~~
 - Add black & isort to handle formatting
 - Use libsonata to provide more of the functionality
   - parsing config files
   - accessing data
+- Circuit validation changed to be more config-driven
+  - it now only validates objects defined in the circuit configuration file
 
 Removed
 ~~~~~~~
+- non-BBP Sonata circuit validation
 - NodeStorage & EdgeStorage classes
 - point_neuron support