The Stacks project

Try to use L/K notation for field extensions

We could also try to consistenly use "field extension" and not just
"extension" and consistently use "ring extension", etc.

Two fixes for varieties.tex

Thanks to Keenan Kidwell
http://stacks.math.columbia.edu/tag/0360#comment-766
http://stacks.math.columbia.edu/tag/04KT#comment-767

LaTeX: \Spec

	Introduced the macro

	\def\Spec{\mathop{\rm Spec}}

	and changed all the occurences of \text{Spec} into \Spec.

Tags: added new tags

Varieties: Loos ends

	There is much more work to be done here. For example this
	commit adds the fact that if X is a variety over a field k then
	there exists a finite purely inseparable extension k' of k such
	that (X_{k'})_{red} is geometrically reduced -- and of course in
	actuality the result is slightly more general.

	There is a similar result regarding geometric irreducibility
	which we should add as well, and we can also think about the
	correct formulation of such a result for geometric connectivity.

	Also, in the section on unit groups we have not yet stated the
	consequence that if X is a variety over k and k is algebraically
	closed in k(X) then O(X)^*/k^* is a finitely generated abelian
	group. In particular, this gives the same result for
	geometrically integral varieties.