Adds a HUD for observers
Adds a HUD for rigs and mechs
Adds up/down buttons for AI hud
Add more tg style alerts
Fix some bugs with the tg alerts
Improve icon_states usage by caching it
Redo how respawning works, add a button to ghost hud for it
This adds throw_alert() and /obj/screen/alert, a system that allows you to do custom hud alerts for any variety of things from "You're too cold!" to mecha status indicators for the pilot.
There's quite a few things that actually got replaced; the
fire/oxy/tox/co2 alerts are all now just alerts, as is nutrition. There's also a number of new alerts, such as blindness, highness, legcuffed, buckled, handcuffed, and probably some more I missed; read code/_onclick/hud/alert.dm and see for yourself!
Additionally, a number of tweaks have been done to resisting code, to make it so that there's an indicator when you're buckled or handcuffed, and can just click the alert to start resisting. This includes a refactor that combines the logic for lockers, holders all into one proc, called container_resist().
Also, the health and internals indicator got moved down one tile each. Needed room for the alerts. If we add the oxygen tank action buttons from /tg/ and remove the internals indicator, the health indicator can go back where it was originally.
Alerts, pictured in the top right.

Fixes auto blindness and no click on 510 servers, lessens the lag of
mesons and material scanners, and I suspect the general speed as well.
I only made it work for Polaris (and by extention, to our server, Eros),
and adapted it a bit.
Ported from:
7c2cc890ab
HUD positions are now relative the client view screen edges instead of absolute.
We don't currently use custom client view ranges, but this potentially makes it more reasonable to implement (an example is a new short sighted species of ours).
Port of https://github.com/d3athrow/vgstation13/pull/5984.
This should have little/no gameplay effect right now, just paving the
way for directional lights.
Replaced handle_rotation() on buckly things with this.
Signed-off-by: Mloc-Argent <colmohici@gmail.com>