Changed the API of the red-black tree after re-reading the exercise, so that it would fit to its requirements.
Changed deleted to be a pointer to the actual key stored in the tree, so that it could be freed.
We could have actually freed the key in the remove function, but I think that whoever allocated it should free it.
Added some documentation
Added the quit function and a macro for it, changed the API function names so that menu would be a prefix
Added the main implementation of the exercise - all factory operations according to Pavel's implementation suggestion, besides CheckBox.
Added the UI for the program and the build tool.