Menu: Made inventory item category be grayed out and unselectable when there is no item in that category.

Fixes #402

I also moved the handling of the key items category back to the gobal inventory manager
where it belongs and did a few code and API cleanups.
Made the minimal text scrolling values quicker.

In order to help with the confirm key bashing problems with dialogues.
I tested it only ten minutes and I already love it. :)
Adding the transform2d class.
Updating the CMake build system to reflect the new files.
Incorporating Logzero's changes into the newer code base.
Some minor updates to the transform2d class.
Prototyping a programmable graphics pipeline.
Adding a sprite class.
Implementing image rendering with the programmable graphics pipeline.
Working around an issue with rotations.
Removing an unused file and updating the CMake build system.
Removing unordered maps for compatability.
Removing the newer C++ features for compatability.
Adding GLEW to the *nixs.
Updating a comment.
Attempting to add GLEW to the build server.
Adding FindGlew.cmake.
Adding the GLEW includes and libraries to the CMake file.
Updating the degree / radian issue.
Fixing some warnings from Cpp Check.