Add different wait for frame behaviour (discard/repeat)

[jhnnslmk]

Right now vvvv is automatically running at 30fps if the capturing camera was delivering 30fps ....

Another wild guess would also be, that vvvv doesn't discard frames yet if the camera would capture at a higher fps than vvvv is currently running at. There should be a setting to discard excess incoming frames instead of buffering them