Added code to set the Qsl Sent status checkboxes other than Queued
and Requested to unchecked, and to disable these checkboxes.
Added code to disable the include checkboxes for any QSO whose Qsl
Sent status is not Queued or Requested. Modified
DisplayQsos.IncludeAllQsos to check the include checkboxes only for
those Qsos whose Qsl Sent status is Queued or Requested.

These are the code changes for issue #131.