- disabled xfeature2d dependency for java wrappers
- fixed java wrappers build after cmake rerun
- disabled opencv_ml tests temporarily
- fixed Imgproc usage in java tests

If both Python 2 and Python 3 are found, then build bindings for both of
them during the build process.  Currently, one version of Python is
detected automatically, and building for the other requires changes the
CMake config.

The largest chunk of this change generalizes OpenCVDetectPython.cmake to
find both a Python 2 and Python 3 version of Python.  Secondly, the
opencv_python module is split into two modules, opencv_python2 and
opencv_python3.  Both are built from the same source. but for different
versions of Python.

Simle Java test for computeCorrespondEpilines added.

small matrix becomes the same after shuffling

* Drop some low level API
* Remove outdated overloads
* Utilize Input/OutputArray

This follows SURF changes in 1f261c2f

This fixes java tests failing with new jpeg versions