Non-drone silicons now have access to a basic security xor medical hud.

Leaving this up for code review and dev-comments, should it be voted desirable. The relevant discussion and poll is found [here](http://baystation12.net/forums/viewtopic.php?f=5&t=11162&view=viewpoll).

* AI and borgs can now select to have a basic security or medical overlay (or neither) but not both at the same time.
* Activating a proper security/medical hud that security/medical borgs have access to overrides these basic variants.
* The basic security hud only offers the work-assignment icon if an id is equipped. This excludes displaying warrant, loyalty implant and other statuses, nor does it grant access to changing warrant status.
* The basic medical hud only displays the health bar, and only if suit sensors are set above binary mode. To avoid displaying any diseased status the dead/alive icon also had to be excluded.
* This is more or less the same information already made available by crew monitoring consoles, only conveniently accessible when observing relevant crew members.

I felt the health bar alone would give a decent enough indicator but perhaps some refactoring could be made to separate alive/disease status if desired.

![Basic medical hud](https://www.dropbox.com/s/scqfmp1faacnm8e/AiMed.png?dl=1) ![Basic security hud](https://www.dropbox.com/s/w7a2qz78ax9h694/AiSec.png?dl=1)
Normally the list of mobs to get HUD-status from is acquired using view(Turf) where the turf is that of the HUD-using entity, as in a couple lines up (and used in line 11 & 31)
However, this doesn't work very well with the AI eye which is quite likely to be behind a wall or otherwise in an unseen turf hence the method of looping over all mobs and checking their distance instead.
Comments and thoughts about performance concerns?