Add serialization to ModuleType
Validate a ModuleType's schema

It would be good to be able to inform the creator of a module type that
the schema they are enforcing for the module options is not valid.
Add endpoint to list and filter ModuleType objects

As with our other filters this is case insensitive.
Add endpoint to create a module type
Remove some left over logging
Add serialize function to Module model
Add endpoint to add modules to a dashboard
Add list modules for a dashboard endpoint
Merge pull request #205 from alphagov/add-a-module

Add and list modules for dashboards