Minor code documentation tweaks for BXGamebox documentation APIs.
Fixed spurious error when trying to trash a documentation file that no longer exists.
Replaced convoluted (and broken) code for monitoring filesystem change notifications, with a much simpler system that just invalidates the filesystem and documentation caches whenever Boxer returns from background. Long-overdue renaming of BXFileManager category.
Cleaned up leftover unused 3rd-party code and acknowledgements for them.