Added a bunch of spawning- and editor-related stuff

-Added a feature to make waves spawn in a specific order. Imported
formations will not be grayed out when this is toggled on. Enabling
random formations again will remove all repeated formations.
-Added saving for wave names.
-Everything should be backwards-compatible. Waves made before this
commit will just be named "Wave #" and default to having random
formations.
-Made "new wave" add a new wave at the selected position, rather than at
the end.
-Made the formation previewer in the level editor preview the angle(s)
the formation will spawn in.
-Fixed a bug with the wave/formation lists.