Stop generating global variables for elements in the scripting environment.

This was a bad decision and is being reverted with this commit. This will break existing applications. Use "GTGUI.Server.GetElementByID('MyElement')"
A complete overhaul of the way elements are created in Server::Load().

Previously, elements were creating by creating a big string containing a script that would be executed. The new system uses the C++ API directly. This should be a lot more efficient, but I didn't do any proper speed tests.