Two new validator classes CallsignValidator and
MaidenheadLocatorValidator are introduced and used in the
Configuration and MainWindow implementations.
MaidenheadLocatorValidator supports different lengths and minimum
required lengths with a default of subsquare with square being
required.
The message_aggregator application has been enhanced to show the
current DX call and DX grid as shown in the WSJT-X main window.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6903 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
