Added TestActivity.java for testing passing of JSONObject between
activities, specifically from BuildWorkoutActivity.java
Modified static final member variables from private to protected in
order to have access from other methods within package.
Added public writeJSON() method for converting object to JSONObject for
passing between android Activities.
Modified callback handler which handles IntervalTypeDialogFragment
returned data.

This modification was done to verify that IntervalWorkout Object could
be passed between Activities.