ZENGINE: Fix parsed arguments in ActionStreamVideo
ZENGINE: Remove Graphics::Cursor inheritance and remove extraneous methods
ZENGINE: Change CursorManager to go through CursorMan instead going directly to OSystem

This had to be done so the cursor didn't disappear after the user went to GMM or debug console
ZENGINE: Remove extraneous _needsScreenUpdate bool
ZENGINE: Create methods for converting screen coords to image coords