[UI] Add a Diff button to the Apps on the home screen

[rolandkool]

Summary

Add a Diff action button to each Application on the main screen.
Currently, each app has three 'shortcut' buttons: Sync, Refresh and Delete
Adding a Diff button (or replacing the Delete button with a Diff button) would be useful

Motivation

We don't have autosync enabled and like to review changes before triggering a sync. However, this requires clicking the app and then clicking the diff, while for doing a sync, you can do it directly from the main screen.
Also, how useful is it to have the delete button there. Deleting an app is not something you do that frequent to warrant it a shortcut on the main screen (IMO). In addition, we have made the UI read only, so the Delete button can't be used anyway. I'd rather have a Diff button there to improve our workflow.