General cleanup
Pruning of #includes in ParleyPracticeMainWindow
Seperation of mode specific construction from the generic construction -- this will make new mode creation easier
Renaming of some poorly named signals/functions
Slight change of design -- the window now keeps pointers to the non-GUI-dependent/integral classes, which aided the ctor seperation.

At this point, my plan for implementing multiple modes is to add a setup<ModeName>() function, and call the appropriate one based on prefs.
Another option is subclassing ParleyPracticeMainWindow for each mode, but I think that would be more effort than it is worth.