This change fixes a compiler warning and changes the way a PPRScheduleTi...

...me computes its description string.

PPRScheduleTime.m - use a DateFormatter etc., rather than a crude stringWithFormat;
PPRTestIIntialiser.m [sic] - fix the warning;
PPRScheduleTimeTests.m - added, for a crude test.
Currently in PPRScheduler it captures the current calendar on init and this is used in its date calculations. PPRScheduler is a singleton and could accessed in this routine. In testing, we could assert different calendars by setting the calendar property in the singleton. Then we "duplicate" the calculation and check it matches. That being said the "english" test would also be necessary as a "fixed point".