Allow to build samples via OpenCV binaries from distribution package
(find_package with OpenCV_DIR).

* fix path to libraries in Android SDK
* allow to link to opencv_java.so as Android.mk does

To link to opencv_java.so you can either change your cmake to find OpenCV as

    find_package(OpenCV opencv_java)

or pass -DOpenCV_FIND_COMPONENTS=opencv_java to your cmake command

Better variant of OpenCVConfig.cmake generation; several smaller changes in the options section and Android build scripts

 [~] Automatically tracked dependencies between modules
 [+] Support for optional module dependencies
 [+] Options to choose modules to build
 [~] Removed hardcoded modules lists from OpenCVConfig.cmake, opencv.pc and OpenCV.mk
 [+] Added COMPONENTS support for FIND_PACKAGE(OpenCV)
 [~] haartraining and traincascade are moved outside of modules folder since they aren't the modules