Silicon Medical and Security HUDs!

- The AI can now access both Security and Medical HUDs via a new button
on its UI. The Medical HUD requires that the person's suit sensors be set either vitals or vitals + GPS mode. The AI's Security HUD only detects jobs.

- Cyborg HUD modules have been removed in favor of an inbuilt command,
to make it less of a hassle to access them.

- HUD code has been given its own file such that it can be used by any
mob. In addition, HUD users are placed into a list instead of searching
for only humans and checking them for a HUD item. This is to make it
easier to expand.

- Security HUD messages can now be received by any mob using a SecHUD. The icon is now a set of handcuffs.

New AI button and Sec HUD message: 
![screenshot 2014-08-21 23 03 01](https://cloud.githubusercontent.com/assets/4955510/4006651/7b73f9f6-29b1-11e4-9069-439b853a0913.png)

*I plan to expand the HUD broadcast feature to Medibots as part of another PR, as bot code is outside the scope of this one.*
Will be faster to replace this if() and += with

sec_hud_users |= M

Do the same with the med HUD. Actually, this is a good sign that having to change two places to make a single change is bad and that the code is duplicated. Put the code into procs and have the blah_hud_users list inserted as an argument to a proc.