1.4.1 Updates and improvements to error checking

4.1.1 - Error handling and better support for multiple Ticket Field Manager apps in one account

Updated app to include better and more useful error handling. 

The app will also use the metadata store across apps to cache REST API calls to the /users/{id}.json end-point (for current user). This will help reduce save hook timeouts. The app will however make calls to the /users/{id}.json on App.activated to ensure data is up-to-date
the `done()` is the same as the previous one, this should be extracted to a callback.