fixing cap_pvpapi interface

This PR tries to fix the following 3 reported issues
- http://code.opencv.org/issues/3946
- http://code.opencv.org/issues/3947
- http://code.opencv.org/issues/3948

Basically it enables use of monochrome AVT cameras AND lets the initialize wait long enough since newer cams have a longer initialization time!
The bug reporter will join also. I think this is incorrect. My Manta is a monocrome camera and returns Mono8 here. This should thus be set to true and false in the 16 bit case. Considering the Proscilla actually uses 16 bit to store a bayer pattern, this is completely normal.