super.onPause() call moved to begining of onPause method according Google recomandations.

FpsMeter class removed from Image Manipulations and Face Detection examples as unused code.

All samples use application style in android manifest instead of system calls in onCreate event now.

- Adding Android SDK/ADT r21 compatibility;
- fixing stl headers path for new ndk;
- fixing native API level for Android projects

Memory leak in color-blob-detection sample fixed;
Default face size in face-detection is set to 20%;
Error handling improved;
Some possible mat leak fixed;
Manager verison and engine interface version incremented to fix incompatibilities;
Docs updated;

Some unification done to simplify camera switching.

(cherry picked from commit 067744d0)

(cherry picked from commit bd12f636)
Signed-off-by: Andrey Kamaev <andrey.kamaev@itseez.com>

(cherry picked from commit 47b96407)
Signed-off-by: Andrey Kamaev <andrey.kamaev@itseez.com>

Android samples are updated: onPause()/onResume() release/open camera, a message is shown on camera open error, minor fixes in code and resources