Add user roles and permissions to API endpoints.
Expose permissions to client; Fix 403 error.
Fix merge conflicts.
Add Trend model and API controller; basic CRUD tests.
Merge enable/disable; fix tests.
Share user permissions code between server and client.
Use mixins to share User class between client and server.
Merge branch '1214_user_authorization' into develop
Merge branch 'develop' of github.com:TID-Lab/aggie into 1126_trend_controller
Merge branch '1126_trend_controller' into develop
Merge branch 'develop' of github.com:TID-Lab/aggie into 1234_session_api_endpoint