OpenCV Manager verison incremeneted;
Docs and tests updated accordingly;
COnstant for Manager initialization added.

Old paths can have problems with cross-compilation

Native activity build warning fixed;
Logcat messages for JavaCameraView updated (Bug #2876);
Some fixes for feature #2893 done.

Issue #2868

Based on pull request #685

Issue #2820

Set ptr to NULL, so this method can be called repeatedly. This fixes a crash after unplugging web cam and trying to re-scan the cameras.

command line option '-Wsign-promo' is valid for C++/ObjC++ but not for C [enabled by default]