add function interface in photoeffects.hpp
Add function fadeColor in photoeffects.cpp
Add test
correct name of function
add a new version of the files.Fade Color
Empty emplementation of the fade color  filter (src/fadeColor.cpp) and fake test (test/fadeColor_test.cpp)
Merge master with branch.
Merge pull request #7 from DolotovEvgeniy/FadeColor-implementation

dummy color fading filter implementation
Merge upstream updates into the branch.