List: Use ic_action_favorite instead of btn_star.

The icon is from the Action Bar Icon Pack:
https://developer.android.com/design/downloads/index.html
Action Bar Icons are probably too big for use in the grid items,
but it's a start.
Use ic_action_accept for the check mark.

This is from the Action Bar Icon Pack:
https://developer.android.com/design/downloads/index.html
List: Use ic_action_upload to indicate that items are uploaded.

This is from the Action Bar Icon Pack:
https://developer.android.com/design/downloads/index.html
This really looks more like an action than a state, but it's a start.
List: Move the favorite marker to the right because it is not common.

And remove incorrect parameters.
QuestionFragment: Use the Favorite action icon.

Though the menu doesn't show it anyway. Still, maybe some UI shows it some time.