OpenCS settings

The Subview section is not yet implemented, but I would like people to try it out and provide feedback comments please.  There are some debug statements still in there, please ignore them ;-)

Unfortunately I couldn't make use of existing settings code by graffy76 (couldn't work out how to use the settings framework with Qt Designer generated header file)
I don't agree that it does no harm. Showing available display modes in the window resolution list would suggest that this setting requires display mode changes, which is not the case.