Hail to the firefighter! Content package.

Huge content package:

Firefighter profession.
Firefighter zombies.
Firefighter zombie item groups.
Firefighter tools: fire axe and Halligan tool.
Firefighter/first responder gear: emergency oxygen cylinders which can treat smoke inhalation and asthma - in two sizes.
Firefighter gear: firefighter helmet, mask, and belt, turnout coat, pants, and boots. Full nomex suit including gloves, stockings, and hood plus full-coverage entry suit.
Firetruck items overhaul with new stuff integrated right in.
New book: A History of Firefighting - skills and new recipes.
New material: Nomex, fully integrated and usable.
New recipes: some can be learned from firefighter book.
New survivor suit: survivor firesuit - armored flame-resistant bodysuit.
Revamped zombie_cop item groups, with an improved weapons group plus a new general equipment group.
Recipe integration of new materials and equipment in extant recipes.

Plus a few minor formatting and item spawn fixes here and there.

Contains many of the remaining goals in issue https://github.com/CleverRaven/Cataclysm-DDA/issues/3069 plus a fair bit of other stuff that I came up with along the way.