Implementation detector and selector for IPP and OpenCL;

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;
Merge pull request #3332 from lupustr3:pvlasov/implementation_detector
Basic doxygen documentation support

- updated existing Doxyfile.in
- added corresponding cmake instructions
- added some specific files (layout, icon)
- clean existing doxygen warnings