Custom commands

[Babreakfast]

• Added support for creating and executing custom commands
• Added support for creating command templates of the three different command types
• Added migrations to properly transition from the legacy command templates in the database to the new version (not that it really matters as we've been storing them in JSON)
• Added proper campaign template persistence service that would actually store the templates in the db and not crash like they used to
• Added import functionality for campaign templates
• Refined the export functionality for campaign templates
• Added a system command definition catalog to provide the schema definitions for the system commands as defined in the datamodel.

This still needs to have the datamodel version bumped up once the datamodel actually gets approved/released.