TODO:
 - Callback on tree item select
 - Clicking on an already selectecd element starts rename 
    - Will likely need some kind of check to ignore double-clicks?
 - Context menu with rename
 - When edit box is initially opened, focus on it
 - Delete with Undo/Redo support
 - Drag and drop
   - If a mouse drag is detected DragAndDropManager is activated
   - Element is not removed from its original position until drag is complete
   - Dragging over an element will make a highlight box appear around it
   - Dragging between elements will make a thick line appear between them
   - Releasing the drag changes the element parents
 - Auto scroll
    - Sliding over top or bottom of the tree view while dragging an element will search GUIElement parents to find a ScrollArea. If it finds one it will attempt to scroll up or down.

MenuBar problems:
 - Mousing over a sub-menu hides the parent sub-menu
 - Clicking the top menu item closes and immediately opens the menu again (it should only close it)
   - Something similar probably also happens with ListBox

 Other:
 - When dragging in tree view automatically expand mouse over elements
 - Ability to select and drag multiple elements
 - "Ping" effect
 - All operations should be undo-redoable
 - Context menu with copy/paste
 - Copy/Paste/Duplicate
   - This is more of a problem with actual copying of SceneObjects (It's not implemented). I should be able to serialize, and then de-serialize with a new parent as a form of copy.


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LOW PRIORITY:

Shoutcuts ideas:
Remove Cut/Copy/Paste/Undo/Redo/Rename/SelectAll and similar shortcuts from InputCommands. Instead send generic shortcut commands whenever user presses some key (with shift/ctrl/alt state).
 - I will need some kind of generic shortcuts at some point so there is no point that Rename is hardcoded to F2
 - I should also add a GUIShortcutManager, as a centralized place for dealing with shortcuts (so that I my edit them at a later date)
  - TODO - Figure out how would this work. How would the centralized system know all of the UI shortcuts? Probably register them somehow on program start?
 - This shortcut system would be separate from the input manager, and would not be meant for in-game use