V03 issue752 2 flowcb/scheduled was not working with the *scheduled_hours* setting. re-written to address that and other issues.

[petersilva]

fixing #752

• it now works for multiple hours in the day.
• it is based on building a list of appointments, once per day, then waiting until each one.
• code now uses python datetime module using datetime, time, and timedeltas (like sarracenia durations.) datatypes.
• notice that housekeeping doesn't run when waiting ... hmm... desirable or not?
• output much clearer now.

Also:

• added support to interrupt sleeps for housekeeping intervals, so that happens now.

[petersilva]

@gcglinton you might want to try adding unit test to this branch? the new implementation is much easier to test.

[tysonkaufmann]

Code looks good - unit testable - Peter has confirmed functionality