Revised chapters "Examples", "Descent", "Algebraic Spaces"

I attach a proposed revised version of the chapter "Examples"
from the Stacks Project. I added another example by Hironaka,
showing that projective morphisms do not satisfy descent
in the fpqc topology on schemes. I modified the earlier example
by Hironaka (showing that projectivity is not Zariski-local)
to match the notation in this new example.

I also attach revised versions of the chapters "Descent"
and "Algebraic Spaces", with brief links to the new example.
Stop parse.py from complaining too much

-- the \section{...} command had better be on one line because I am not
sure what the consequences will be for the scripts used to munge the
stacks project data if the title spans two lines. As a consequence we
now have a line in examples.tex which is more than 80 characters long.
As far as I know none of the python or php scripts actually depend on
having 80 characters per line. (I couldn't think of a suitable shorter
title of this section.)
-- We require $$ to be alone by themselves on a line.
-- Fixed a reference.
Tags: Added new tags

Also fixed two references