added the ability to create and remove entities from the tree panel
added PANEL:OnRightClick event
added callback argument to PANEL:Animate
added gui2.CreateMenu(options, parent)
added minimize and maximize functions
added icons to menu
cleanup
added TREE:GetSet/SelectedNode()
added name property
set the sun light entity name to "sun"
don't store cached textures in a weak table...
fixed entities not removing children properly