uniformize dialog names

Fltk/FlGui.cpp

Fltk/extraDialogs.cpp

Fltk/extraDialogs.h

Fltk/fieldWindow.cpp

Fltk/fileDialogs.cpp

Fltk/fileDialogs.h

Fltk/graphicWindow.cpp

Fltk/menuWindow.cpp

Fltk/messageWindow.cpp

Fltk/optionWindow.cpp

Fltk/projectionEditor.cpp

Fltk/solverWindow.cpp