Added new feature and bug fixes.

Added Feature:
"Total Workout Time" indicator on Edit screen so that the user can see
the workout time accumulate/decrease as they add/delete exercises.

Bug Fixes:
-If you open an existing workout, then choose the "Save and Begin
Workout" option when you click "Finished", when you start the workout,
it will be at 100% and the total time left will be 00:00:00

-If you Open an existing workout, then go back to the Main screen and
then Edit a workout, the Preview window will contain exercises from the
previous workout loaded.