Just some very very basic groundwork for undo/redo.
The first of many commits completely reworking the way the sub-editors work in the main editor.
Silence a few warnings.
Add an enumerator for the various asset types.
Add support for retrieving asset types from the extension of a given file name
Fix compilation error.
More groundwork for the new editor system.

This commit adds initial implementations of Editor::OpenFile(), Editor::CloseFile(), Editor::ShowFile() and Editor::HideCurrentlyShownFile(). These methods are going to do the main work and then eventually post events to the scripting environment.
Fix warning.
Add Editor.OpenFile(), Editor.CloseFile(), Editor.ShowFile() and Editor.HideCurrentlyShownFile() to the scripting interface.
Make a few improvements to the constructor or sub-editors.
A small refactor in preparation for switching over to the new editor system.
More groundwork for the new editor system.

This commit creates a tab GUI element for each sub-editor via the C++ code. Basically, I want as much of this file management stuff to be moved over to the C++ interface, with the scripting interface being mostly simple 1:1 wrappers, if anything.
More work on the framework for the new editor system.

This system has files being opened, closed, shown and hidden using the new system now. The next major part is to integrate the actual editors.
Have the scene editor use the new editor system.
Have the text editor use the new editor system.
Have the text editor use the new editor system.
More fixes for the new editor system.

This commit comments out some now unused and unneeded code. This will be removed properly later on when this new system is done. The main purpose behind doing this is to catch hidden bugs.
Fix the menu button enable states as the state of open files are changed.
Comment out unused code.

This will be removed in future commits, but will be kept until the new system is fully implemented and tested.
Add framework for the new image editor.