opencv: import from oe-classic and upgrade to 2.3.1

OpenCV <= 2.2 won't compile on oe-core due to the lack of v4l1 headers, and therefore wasn't included in this patch.
Also, the support for newer cv2-style python bindings is a bit hacked up at the moment due to the way OpenCV detects the Python version and Numpy headers (see 0001-Fix-CMakeLists.txt-numpy-detection.patch). In particular, it requires the native & target python to be the same version and have similar site-packages directories, which is true at least for now in OE.

Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>