use new abstract interface and hidden implementation

- Gaussian blur;
- CascadeClassifier;
- Blenders in stitching module;
- Laplacial pyromids in stitching module.

quickly corrected the previous refactoring of features2d: moved from set(SOME_PROP, val) to setSomeProp(val)

OpenCV with the refactored features2d compiles! contrib is broken for now; the tests are not tried yet

OpenCV with the refactored features2d compiles! contrib is broken for now; the tests are not tried yet

IPP can be switched on and off on runtime;

Optional implementation collector was added (switched off by default in CMake). Gathers data of implementation used in functions and report this info through performance TS;

TS modifications for implementations control;

When we have similar matrices in input, then algorithm returns matrices
with NaN values.

fixed dependency of stitching module on xfeatures2d module as optional
fixed the initModule_xfeatures2d function that was called in module stitching since it is in another namespace than the standard cv one.

1. someMatrix.data -> someMatrix.prt()
2. someMatrix.data + someMatrix.step * lineIndex -> someMatrix.ptr( lineIndex )
3. (SomeType*) someMatrix.data -> someMatrix.ptr<SomeType>()
4. someMatrix.data -> !someMatrix.empty() ( or !someMatrix.data -> someMatrix.empty() ) in logical expressions

- Fix both stitching_detailed.cpp sample and cv::Stitcher.