Engine improvements: GtkGLExt no longer used, new TCastleInspectorControl, loading op

[DP News-Robot]

November/December engine improvements: We no longer use the GtkGlExt library on Unix. It was not necessary (we had a code to initialize OpenGL directly using glX on X11, and it is simpler). And this way user has one less library that needs to be installed before our application can be run. Loading optimizations: The TCastleTransform …