The Stacks project

Two typos in homology

THanks to jose and LSpice
https://stacks.math.columbia.edu/tag/010I#comment-7757
https://stacks.math.columbia.edu/tag/010I#comment-7953

Small changes to homology

homology.tex: latex normalizations

homology.tex: define morphisms of extensions

Not sure if there is an abstract-nonsense reason why
it is the only reasonable definition; I don't see one,
so I added an explicit definition.

C should be B

Thanks to Fred Rohrer
http://stacks.math.columbia.edu/tag/010J#comment-2376

LaTeX: \Ob

	Introduced a macro

	\def\Ob{\mathop{\rm Ob}\nolimits}

	and replaced any occurence of \text{Ob}( with \Ob(. There are
	still some occurences of \text{Ob} but these are sets, not the
	operator that takes the set of objects of a category.

Started tags infrastructure

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

More changes to simplicial and homology