Fixes issues:
#2632 Fire Issues (Fire doors work, Flamethrower reverted to making a flamethrower liquid fuel subtype, flame grenades now make a puddle of welder fuel that is lit aflame with napalm)
#2630 (The code has been calling (turf).temperature_expose when it was supposed to be hotspot_expose), #1865 (aqain)(Added a check to remove trace gas fuel under a certain point).
Also: added a flashpoint value for plasma, which is the temperature at which it self-ignites (Currently 246C or 519K which is equal to gasoline)
Partial-tile firedoors now default to full-tile firedoors as the part-tile ones were breaking ZAS zones entirely.  Possible cause of #2627 and maybe #2451, but those need tested and I did not have time.
Merge pull request #2644 from SkyMarshal/master

ZAS fixes: #2632 #2630 #1865
Version 11 of RowtreeStation.dmm
Mixing napalm is incredibly broken with ZAS / not found on our wiki because it's a "secret recipe" so I figure let's just comment it out.
Merge pull request #2648 from Asanadas/master

Misc: Rowtreestation v11, commenting out Napalm making.
Fire update.  Should now burn out after a time, and temperature varies on a number of conditions.  Fixed a runtime, and made fire work in canisters.  Ingame modification of ZAS is now possible again.  Firedoors now remove duplicate firedoors on the same turf.
Napalm can now be made, due to fire changes.
fuel is now a bit less derpy.  Napalm produces volatile fuel, and less of it.  Fire consumes more welding fuel.
Compile fix.
Fix posibrain not turning off if no candidate

The reset proc was checking for the presence of a brainmob, while one
was created in the constructor. It should rather check the presence of a
key
comments out suethecake's gun due to having a weapon's ban
Merge pull request #2654 from Ravensdale/master

Custom item fix
Merge pull request #2652 from SkyMarshal/master

Fire fixes and improvements.  Note: May need fine tuning.
Add check forposibrain without brainmob

This should never happen, but check nonetheless.
Merge pull request #2653 from Jupotter/master

Fix for posibrain not turning off
Fix a wrong null check in posibrain

A wrong nullcheck that prevent posibrain searching for a player
Merge pull request #2656 from Jupotter/master

FIx posibrain unable to be started
Removing the captain spawning in with his space suit armor.
Bugfix: Adds in a check to make sure atmos code has been loaded before trying to generate, preventing some runtimes.

Tweak: Removes captain's armour from spawn code.

Tweak: Captain's PDA now spawns with messenger on but is now undetonateable.
final tweak for cap's PDA to do as advertised.