Add mode dependent working frequencies

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

AudioDevice.cpp

@@ -1,18 +1,5 @@
 #include "AudioDevice.hpp"
 
-#include <QMetaType>
-
-namespace
-{
-  struct init
-  {
-    init ()
-    {
-      qRegisterMetaType<AudioDevice::Channel> ("AudioDevice::Channel");
-    }
-  } static_initializer;
-}
-
 bool AudioDevice::initialize (OpenMode mode, Channel channel)
 {
   m_channel = channel;