Move all the phabricator stuff to its own machine.

Summary:
Everything else on internal-webserver (toby) stays.  Mostly this
involved moving files as appropriate, and splitting up setup.sh.  I
also took the opportunity to audit install_phabricator() in setup.sh
and fix some old stuff up.

Have https://cr.khanacademy.org redirect to phabricator as well as http://.

Also, fixed a few comments based on review.

Test Plan:
Fingers crossed.  Once this is landed I'll try creating a new
machine on ec2.  (What I'll probably do is create a new toby machine,
and turn the existing toby into phabricator.ka.org, since I don't want
to worry about messing up phabricator.)

(None new)

Reviewers: alpert, chris

Reviewed By: alpert, chris

Differential Revision: http://phabricator.khanacademy.org/D14739