Added custom video frame size to qtcoin

Replaced VIDEO_WIDTH and VIDEO_HEIGHT with variables in qtcoin class so
that the rendered frame size can be adjusted. viewerrecorder now sends a resize command to the renderer so that resolutions other than 640x480 work correctly.

Tested on ubuntu 12.04 without incident, though the thread safety of changing the video size is unclear.  As long as the video size is adjusted before recording starts, everything seems to work ok.