Adds emergency response team verb

* Adds a verb for (b)admins in "Special Verbs" that lets you spawn in an
emergency response team a la deathsquid-button
* Spawned-in ERTs can choose their own ridiculous name
* Command alerts, because everyone loves those
Adds the "Response Team" landmark to the ERT room
Changed the way ERTs are selected

* Ghosts get a pop-up thingy that asks them if they want to be
considered
* Ghosts that're antag-banned and/or jobbanned from security officer are
exempt
* 30 second timer because timers are !!FUN!!
Merge pull request #2985 from Kilakk/bleeding-edge-freeze

Adds emergency response team verb