Don't let Bungee run in dirs with ! in name.

Java uses ! to indicate a resource inside of a jar/zip/other container. Running Bungee from within a directory that has a ! will cause this to muck up.
Correct a typo in Spawn Object rewriting
Fix uniqueId returning null in LoginEvent
Handle objective value changes. Although the client *shouldn't* be using this for any sort of keying, it may indeed be. Closes #1116 awaiting testing.
Clarify PreLoginEvent