Precompiled headers support on Linux (CMake)

[Witek902]

• [x] All PCH.hpp files should be treated as precompiled headers (compiled by PCH.cpp), as on Windows.
• [x] Verify compilation speed.
• [x] There should be cmake definition that disables PCH.cpp compilation, turns off the all PCH and makes that PCH.hpp does not include anything - to verify that all source files and headers are self-contained (do not have PCH.hpp dependency).