* Adds hacking tool.
In normal mode a hacking tool acts and functions just like any multitool. Use a screwdriver to toggle between normal and hacking mode.
Hacking attempts will take 20 +(0 to 20) seconds (triangular distribution, averages at +10 seconds).
Once an airlock has been successfully hacked the user will have full access to the door operation interface normally restricted to silicons.
A hacking tool will remember the last 6 to 8 hacked airlocks. No time is needed to again hack remembered airlocks.
Once the limit has been reached the least recently accessed airlock is forgotten. Hacking a remembered airlock will update the last accessed time.
Also adds a basic observer/listener pattern implementation to, for example, make it easier to catch when objects have been destroyed and clear references.
* Corrects and adds more sanity checking.
* Adds hacktool to uplink devices
``/mob/dead/observer`` -> ``/mob/observer/dead``
``/mob/eye`` -> ``/mob/observer/eye``
Reason being that they are similar in that they both don't interact with
the world in any way. Some procs were shared, some checks as well, and
it overall makes more sense this way. Plus, there were no ``/mob/dead``
mobs.
