Working frequencies are mode dependent and a reset to defaults button
has been added.
Also re-factored much of the model and item delegate code to simplify
several of the model implementations. Introduced a single routine
called from main to register the custom types with Qt.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@5453 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
