Front/back camera constants semantic for Android fixed (Bug #2839).

Front/Back camera constants' values changed;
Additional camera facing check added for JavaCameraView.
fixing build and lint warnings
Fix a bug found on Intel OpenCL SDK.
use float when sum overflow
Front/Back camera semantic support added to Android VideoCapture back-end.
Merge pull request #843 from pengx17:2.4_stereobp_fix
Merge pull request #844 from bitwangyaoyao:2.4_integral
Merge pull request #827 from apavlenko:fix_android_tutorial1
Merge pull request #800 from asmorkalov:android_cam_idx_semantic
NullPointerException in case of error on opening native camera fixed.
fixing precommit build on ubuntu-64 (now it takes OCL headers from non-default OCL SDK, but libs from default one)
Merge pull request #858 from apavlenko:fix_ocl_build_on_bb
Merge pull request #854 from asmorkalov:android_null_invalid_cam