Refactor the jinja rendering and the redaction as a pipeline of
filters that run as needed.

It works, but needs some cleanup and documentation

When a venv is created, 'click' will now be installed into it.

This also removes the "dd" that was accidentally introduced into the
variable's value in commit 8463ab1fd21e, the same commit that made the
variable unused (I think we can guess the vi-ism that happened here).
So if we're ever restoring this variable, remember to remove the typo.

Hmm, I'm a little leery of putting this here, given the advice in the
log message of commit 45c93c61.  But we already have two docs
depending on it, and I didn't want to leave it sitting as a local
change (I'd meant to commit it and just forgot, and probably that all
happened before commit 45c93c61 was even made).  So I'm committing
it now, on the theory that it's a found dependency, but if we want to
revise our philosophy to be closer to what commit 45c93c61 says, I'm
open to that discussion, and I realize it might result in the
reversion of this change too.

There are two issues here.  First, LaTeX wisdom (and docs) say to load
hyperref as close to last as possible, or you're going to break
things.

Second, loading it here precludes loading it later with different,
conflicting options.  Generally, ots.sty should load things that are
essential.  Put the optional things in subsidiary style files or
individual docs.

Both of these blocks were very common in LaTeX headers at OTS.

In the example LaTeX document, use the new 'ots-sectioning' package,
as per commit 0071eb8b and commit 77066355.

Among OTS's docs that used this unnumbered/numbered sectioning system,
there were two variants (well, really three, but one of the variations
was just the presence or absence of a comment about appdxsection being
"related to CAMH template stuff that is too boring to go into here";
that comment seems likely to be obsolete so I'm not porting it over).
The newer of the two variants was only used in one doc, but that doc
was the most recent one, so what it has is probably what we want:

* Add comment about using "\setcounter{section}{0}"

* Include a colon, so it's "Appendix <letter>:"

Those are backup files or autosave files, and they muck up the build
process, especially if they're a link to a file that doesn't exist.

We had been repeating this command definition in the preamble of all
our LaTeX documents; now we don't have to do that anymore.

Don't print all the possible 'make foo.pdf' commands when there are so
many source files (not all of which are necessarily even buildable on
their own) that the list would be very long.

This is part of a general effort to shift usepackage statements out of
individual .ltx documents and into our common .sty infrastructure.
There are probably other packages that could be shifted too; rather
than do a sweep to find them, I'm just doing it opportunistically.

Move the LaTeX template files and the get_revision script from OTS's
private SVN tree to here.  Rewrite README.md.  Clean up the Makefile,
moving all documentation into README.md removing the "VIEW=true"
feature as discussed with James.

Use spaces instead of TABs for the left-side whitespace on line inside
the shell expression.  Break the first line into two lines, and on all
lines move the continuation backslashes leftward to stay within 80 cols.