removed separate example for reading image sequences and modified starter_video.cpp to better explain the functionality of VideoCapture. I also added a bit more explanation in the documentation of the VideoCapture interface

Conflicts:
	modules/highgui/doc/reading_and_writing_images_and_video.rst
	samples/cpp/starter_video.cpp

starter_video.cpp changed CV WINDOW KEEPRATIO to just WINDOW KEEPTATIO to fix build error

starter_video.cpp hid local functions