* IF a texture was reimported (calling replace as an example), it would invalidate all materials using it, causing plenty of errors.
* Added the possibility to get a notification when a uniform set is erased.
* With this notification, materials can be queued for update properly.
-Used a more consistent set of keywords for the shader
-Remove all harcoded entry points
-Re-wrote the GLSL shader parser, new system is more flexible. Allows any entry point organization.
-Entry point for sky shaders is now sky().
-Entry point for particle shaders is now process().
