Add "Clear Scene" button to SceneBuilder, change behavior of deleted items, add tooltips

[Thirtybird]

currently, the scene builder removes objects from the "scene list" that are destroyed on the table.
Change scene builder to keep those items in the list, but add a button to the GUI to clear out all actors from the scene
add tooltips to all buttons so there's a better understanding of what they do.
remove the "G" button for now because it removes the HeroMod gui interface from your screen when you use it
Pair "Load Scene" button with "Unload Scene" - remove all characters from HeroMod scene