Removal of Custom QtCreator Project Generator Script

So far the recommended way to setup a QtCreator project for Blender was through the build_files/cmake/ script. This would create custom QtCreator project files. @ideasman42 set this up a while ago because of limited CMake support in QtCreator, causing issues for Blender development.

QtCreator seems to have pretty good CMake support now, and it appears to work fine without our custom project files. That means we could remove the script.

Writing this here to ask people to test QtCreator without custom project files. Please let us know if you find issues or have objections. Otherwise we’ll remove it soon.

The old workflow would change a bit: To load the Blender sources as QtCreator project, simply open the top level CMakeLists.txt through the QtCreator Open Project dialog. By clicking on the Projects mode on the left side, you can control CMake cache settings, as through the CMake-GUI.