Added unlockable lockboxes

- Fixed some relative pathing in lockbox.dm
- Added unlockable lockboxes

These are lockboxes I plan to use in fabricators.
They don't stop you from getting to the sweet sweet candy inside, but they do log your name when you unlock one.
You can always emag or emp one to be untrackable as a traitor, though.

http://puu.sh/crs1z/6e4b607a50.png
http://puu.sh/crs2p/4718d79b85.png