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.
Add a method to get the underlying ThreadFactory for use with external libraries
This method was added in the sub-class "Unsafe" in Plugin. This follows the Unsafe pattern used in other parts of the project.
getExecutorService() was also moved into the Unsafe class and the old method simply forwards to the one in the Unsafe class, this prevents plugin breakages.