Merge branch 'develop'

Time to merge in the development on the chapter on fields.

Thanks to the people of the CRing project for writing the
initial version of this chapter. These people are
Shishir Agrawal, Eva Belmont, Zev Chonoles, Rankeya Datta
Anton Geraschenko, Sherry Gong, Francois Greer, Darij Grinberg
Aise Johan de Jong, Adeel Ahmad Khan, Holden Lee, Geoffrey Lee
Akhil Mathew, Ryan Reich, William Wright, and Moor Xu
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The chapter on fields was taken from the CRing project and this
deserves to be explained in the introduction.
Get rid of smallskips

Also changed the bulleted lists by just itemize
Nothing to see here: controlling paragraphs neurotically
Stop using \em in LaTeX
Simoplify some of the LaTeX in etale-cohomology.tex

This will hopefully make 03UG render correctly on the website
Remove use of 01IW from proof of 01K4

Thanks to Keenan Kidwell
http://stacks.math.columbia.edu/tag/01K2#comment-278
D_{QCoh}(X) has perfect generator for X qc + qs
D_{QCoh}(X) has perfect generator; case of algebraic spaces
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New chapter about differential graded algebra

Short term goal: develop enough theory so we can use it to prove the
result that D_{QCoh}(X) = D(A) for some differential graded ring A
when X is a qc+qs algebraic space