Implement missing features in CvCaptureCAM_VFW class.

Implemented missing CvCaptureCAM_VFW::setProperty() member function (handling CV_CAP_PROP_FRAME_WIDTH, CV_CAP_PROP_FRAME_HEIGHT, CV_CAP_PROP_FPS properties).
Extended CvCaptureCAM_VFW::setProperty()/getProperty() functions to handle also CV_CAP_PROP_FPS property.
Minor refactoring of CvCaptureCAM_VFW class.