First pass on experimental change that allows zones to "Sleep"
Added new two-tile hazard door sprites, thanks to Ravensdale, and fixed a derp with the new ZAS sleeping stuff.
Removes the gas mask filtering stuff from gas mixtures.  Moved it into the relevant "life" code.
Fixes #3668, added detection for known implants to the med scanner

doesn't include explosive implants, etc.
Merge pull request #3671 from Kilakk/dev

Fixes #3668, added detection for known implants to the med scanner
Merge pull request #3670 from Faerdan/dev

Nano UI Updates
Merge pull request #3669 from SkyMarshal/airfixes

Zones can now sleep, multi-tile firedoors are sprited, and gas masks no longer have their fingers in gas mixture code...
Merge branch 'dev' of https://github.com/Baystation12/Baystation12 into dev