ENH: DotStim and ShapeStims all now using new coords system
ENH: Aperture and DotStim now support new coords system
FF: new MovieStim draw() method was corrupting color rendering of other stimuli

This was caused by the wrong texture target being left activated
FF: tools.monitorunittools.convertToPix() made more general
ENH: contains() and overlaps() and now use the new unified coordinates

They should now accomodate different units for different objects
event.Mouse has been given a `units` attribute (which reports the win.units)
so that it can also be used automatically in this system.