Add app permission checking to canThis

- Pass permissions loading to buildObjectTypeHandlers to eliminate
shared state
- Load both app and user permissions to check
- Check app permissions if present
- Create apps table and App model
- Move effectiveUserPermissions to permissions/effective
- Change permissable interface to take context; user and app.
- Add unit tests for app canThis checks and effective permissions
Merge pull request #2199 from jgable/canThisApp