mavconn-camera-opencv: set config in non-stereo modes as well

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
PxOpenCVCamera.cc: implement framerate setting

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Merge pull request #24 from koenkooi/fps

Implement framerate setting for opencv