The Stacks project

Reorganize and improve some glueing stuff

Thanks to Jiachang Xu
https://stacks.math.columbia.edu/tag/00EN#comment-3250

Invisible changes

Limit the number of different commands used in math mode

Revised the material in commits Darij Grinberg

Removed the PBW like lemma in commit
b28cd605026f9194c57022c3b301843e52a66f50
Although we should have lemmas like this in the future, it wasn't
necessary for the proof of lemma-finite-finitely-presented-extension.
Instead we moved this lemma later so we can make use of (very
elementary) theory of finite ring maps, thereby reducing to the one
variable case which should be clear to anyone with an undergraduate
course in modern algebra,

Of course this means we *should* add a discussion of the Grobner
basis algorithm and at that point the lemma will be obvious.

algebra.tex: Add a bit of detail and fix a few bugs.

Invisible changes

Part of neurotically trying to uniformize use of latex commands in math
mode.

Started tags infrastructure

	new file:   scripts/add_tags.py
	modified:   scripts/functions.py
	new file:   tags/initial_tags
	new file:   tags/tags

More neurotic changes

Neurotic changes continued

	modified:   algebra.tex
	modified:   constructions.tex
	new file:   scripts/commands.py
	modified:   scripts/functions.py
	modified:   simplicial.tex

Switch from work to home

	modified:   algebra.tex

Large set of changes involving:

	New file homology.tex for homological algebra
	Fixes in file injectives.tex
	Typos by Zach Maddock
	Example by Alexander Palen Ellis
	Proof of commutative square by Kristen Hendricks
	Proof of K_0 local ring by Ian Whitehead
	Proof of standard cover lemma by Andrew Fanoe