Initial commit for Conjugate Gradient method

Implementation is based on
http://www.cs.cmu.edu/~quake-papers/painless-conjugate-gradient.pdf

So far we only have basic interface and empty test. But it compiles at
least.
Refined interface for Conjugate Gradient

Some interface was refined (most notably, the method for returning
Hessian was removed and the method for getting gradient was added as
optional to base Solver::Function class) and basic code for
setters/getters was added. Now is the time for the real work on an
algorithm.
Finish implementing the Nonlinear Conjugate Gradient

Now everything is prepared for the pull request.
Minor fixes

Fix failed builds that opencv's buildbot has got.
Added the copyright statements

Added the copyrights missing in all files that required so.
Add cv::logPolar, cv::linearPolar, and a python example
Fix a bug in the er tree clean-up process (see discussion in https://github.com/Itseez/opencv/pull/1520). It's not necessary to walk the er tree in order to clean up the memory since it's possible to cleanup the regions in the stack just by iterating over the er_stack vector instead of walking the tree structure. This turns out to be safer because the tree structure of those regions may have been modified previously in er_save function.
the first draft of transparent API and new UMat class.
the first draft of transparent API and new UMat class. more files
hopefully, fixed compile errors on Win & Linux; fixed getMatVector() so core & imgproc tests now pass; fixed doc builder errors
fixed some more compile bugs (including Python bindings)
fixed build on Windows
removed refcount field from Mat; that helped to find and eliminate some memory leaks. perf tests should probably pass now
trying to fix failures in tests
fixed crash in Python bindings
yet another attempt to fix test failures
added first very simple test for UMat<=>Mat conversion
fixed whitespace errors
hopefully, the last test failures are fixed now
fixed some bugs in OpenCL branch of UMat implementation; maybe now the tests will finally pass?! (please ;( )