Base change for ring maps essentially of finite type

TODO: Write about morphisms of schemes which are essentially of finite
type. There seem to be several different possible definitions, one of
which is to say that X ---> S is essentially of finite type if X is a
cofiltered limit of schemes of finite type over S with affine open
immersions as transition maps.
Add a bit more precision in more-algebra.tex

TODO: Need to fix usage of depth...
Additional lemma on finiteness of normalization Nagata schemes
Criterion for when map of qcoh sheaves injective
Depth goes down a finite map
Fix statement and proof finiteness result