Mobile API ProtoRPC Updates
 - Mobile API version upped to v9
 - When registering, UUID is now required
 - Individual add/remove favorite/subscription endpoints have been removed. Use update_model_preferences
 - When adding model preferences, pass a model type (see consts/model_type.py)
 - Model type is included when favorites and subscription lists are returned
Add constants for enumeration
Update model enums to match app
Bugfix
Merge pull request #1099 from phil-lopreiato/rpc-updates

Mobile API ProtoRPC Updates