Fix the failed assertion by replacing the GEMM call.

Also random numbers are generated from normal distribution ~N(0,1),
instead of uniform distribution ~U(0,1).

The latest version (5.1.1) of the gnu compiler returns just its major version ("5") when given the "-dumpversion" argument. Gnu compiler developers don't consider this to be an error. A workaround for this case has been made.

now it builds by the command:
`cmake.exe -Wno-dev -GNinja -DCMAKE_MAKE_PROGRAM="path\to\ninja\ninja.exe" -DCMAKE_TOOLCHAIN_FILE=../opencv3/platforms/android/android.toolchain.cmake -DANDROID_ABI="armeabi-v7a with NEON" -DANDROID_SDK_TARGET=21 -DANDROID_NATIVE_API_LEVEL=14 -DCMAKE_BUILD_WITH_INSTALL_RPATH=ON -DBUILD_ANDROID_EXAMPLES=ON -DINSTALL_ANDROID_EXAMPLES=ON -DWITH_OPENCL=YES -DANDROID_OPENCL_SDK=path\to\OpenCL ../opencv`

adding missing images from python tutorials, like chessboard.png, simple.jpg, home.jpg, fly.png, ...

refactored; added Camera2, notify callbacks, front/back maxCamera sizes; disable new stuff if target API < 21

Catched on Ubuntu 12.04 with FFMPEG:
  codec:                     YES (ver 53.35.0)
  format:                    YES (ver 53.21.1)
  util:                      YES (ver 51.22.3)
  swscale:                   YES (ver 2.1.0)
  resample:                  NO
  gentoo-style:              YES

it is new'ed but never deleted. However it does not need to be global or
heap allocated in the first place.

Corrected typo and unused imports

OPENCV_IPP env var now allows to select IPP architecture level for IPP9+;
IPP initialization logic was unified across modules;