The Stacks project

Better handling invertible modules

Of course an invertible module should be defined as a module such that
tensoring with it is a self-equivalence on the category of modules. This
doesn't change a thing beyong the definition, because we usually are
working on locally ringed spaces or topoi where an invertible module is
the same thing as a locally free module of rank 1.

Started tags infrastructure

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

A bit more stuff on constructing schemes, specifically
relative spectrum
vector bundles
Proj of a ring
relative Proj
projective bundles

	modified:   algebra.tex
	modified:   coding.tex
	modified:   constructions.tex
	modified:   modules.tex
	modified:   morphisms.tex
	modified:   schemes.tex
	modified:   sheaves.tex