Add optional display of event end times

This pull request adds control over the display of ending times for events.

    In the code      In the user interface
    supressEndTime   Show Event Ending Times
       never            Always (the default)
      always           Never
      hour             If the event is one hour long
      hourorless       For events longer than one hour

The second option only shows beginning times, always suppressing end times.

The third option shows beginning times without ending times for events lasting exactly an hour.
Events shorter and longer than one hour have both beginning and ending times shown. The purpose
of this choice is to de-clutter the display for calendars having most events lasting an hour, only
showing the exceptions.

The last option only shows end times for events lasting longer than an hour.

This pull request should be handled before #67. It builds on the code that adds date range selection #66 and more useful formats for dates  #65.