The Stacks project

Add missing version of flatness criterion

Noetherian case for algebraic spaces

Added two new chapters

	Of course these are virtually empty at this point. The idea of
	the chapter "criteria" is to put there the stuff which allows
	you to prove that a given stack in groupoids is an algebraic
	stack. The idea of the chapter "quot" is to put there existence
	results for Quot and Hilbert schemes/spaces.

Where is a relative map an isomorphism

	If X ---> Y is a morphism between flat proper families of
	varities then it is often useful to know that the set of points
	in the base where the map is an isomorphism is open and that its
	formation commutes with arbitrary base change. In this commit we
	prove a maximally general version of this. (If it isn't
	maximally general, then please email.)

Criterion for flatness per fibre + application

	Exactly like for schemes...