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.
I think we should use the current calendar rather than gregorian. I think this is set up in the locale.