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!
Adjusting the package size with a static value is dangerous, not all systems and ethernet cards support this. This is mainly done to avoid overhead, probably by the original author. It will work on some systems but fail miserably on others. Just let the standard package sizes be used and ignore the overhead it creates.