Added some boilerplate to the rendering system. It's now impossible to start...

Added some boilerplate to the rendering system. It's now impossible to start new rendering cycle if the previous one hasn't finished yet.
Changed: OS name, GPU name and GZDB revision info are now added to the exception text and GZCrash.log.
Fixed, cosmetic: toolstrip separators visibility must be updated when resizing the main window.
Internal: removed Plug.DisplaySize, Plug.DisplayLocationAbs and Renderer.ViewportSize. The same data can be accessed from anywhere using General.Interface.Display.Size and General.Interface.Display.LocationAbs. Also Plug.DisplayLocationAbs returned incorrect coordinates...