Apps : Category attributes + model improvement

- #51
- Fix rendering of error message on app-controller
- #48 : function to read categories from JSON file from the server
- #7 : improve model (category, link, email)
- #8 : update view adding app's new properties
Revert "Apps : Category attributes + model improvement"

This reverts commit a44519205637049058b9bf2c2d374d6c73a07e13.
Merge branch 'bayk' of https://github.com/eicnam/Toggle-Play into bayk
Revert "Revert "Apps : Category attributes + model improvement""

This reverts commit 72aa16d2fd94ddb6ae40393e450cc4e3d47cf78c.