Clean up the recording dialogs in ScheduleCommon.

Merge SC::ShowRecordingDialog(), SC::ShowNotRecordingDialog() and
SC::ShowNotScheduledDialog() into SC::EditRecording().  This does make
for a long function, but I find it much simpler to follow with all of
the logic concentrated in one place instead of spread over three.  It
removes a little duplicated code, too.  Also fix some inconsistencies
in the recording status textual descriptions.