Added Method (+ Test) for FitnessExercise.isTrainingEntryFinished().
Added small versions of all exercise images.

Removed unused icon.
Added icon_square_blue and icon_square_green
Implemented a custom ListAdapter for FExListFragment.

So the current status(finished/not finished) of each exercise can be displayed.
Design change for list_row_fex and list_row_fex_done
FExListAdapter: The listview now shows the number of unfinished/missing FSets.