Adds override functionality to class capacity script.
Revert "Disable context processors when rendering e-mail"

Django internally caches the list of functions specified in
TEMPLATE_CONTEXT_PROCESSORS, to save on imports:

https://github.com/django/django/blame/1.4/django/template/context.py#L139

Side effect of the reverted commit: If a comm panel preview is the first
request handled after a code reload, the website will run with no
context processors.

With a testing procedure of sitting on the preview page and refreshing,
this gives the appearance of that fix having worked.

(As MessageRequest.parseSmartText was only ever triggered by the dbmail
cron script, half of this didn't actually need to be reverted for
correctness.)

This reverts commit d9263ef802fa4abc351a69e0425562fd059623e6.
Comm panel: Preview with correct user (try 2).

A second attempt at d9263ef802fa4abc351a69e0425562fd059623e6.

Render the e-mail preview using Django's vanilla Context rather than our
AutoRequestContext, as noted in this comment:

https://github.com/learning-unlimited/ESP-Website/blob/7e32ad7b50/esp/esp/dbmail/models.py#L319
Fixes #586: updating availability when classes are scheduled
Minor fix for teacherquizmodule markCompleted.

It hadn't been saving the program; now it should.
Add message when a user attempts to activate an account that has already been activated.
Fix local updates from dashboard status dialog actions.

Issue #690: "The status button in the dashboard updates the formatting of the class, but not the [STATUS] text."
Move duplicate code into generic functions.
Add classroom/location to dashboard status dialog.
Update the MathJax JavaScript include link.
Merge pull request #712 from learning-unlimited/issue679

Update the MathJax JavaScript include link.
Merge pull request #689 from mgersh/fix-availability-update

Fixes #586: updating availability when classes are scheduled
Merge pull request #663 from benjaminjkraft/change-capacities-script

Adds override functionality to class capacity script.
Merge pull request #676 from pteromys/commprev

Comm panel: Preview with correct user (try 2).
Merge pull request #702 from learning-unlimited/teacher-quiz-fix

Minor fix for teacherquizmodule markCompleted.
Merge pull request #711 from learning-unlimited/issue630

Add classroom/location to dashboard status dialog.
Extend already-activated message with login link
Merge pull request #708 from learning-unlimited/alreadyactivated

Account already activated message
Fix typo in adminclass action for positive status codes
Merge pull request #710 from learning-unlimited/issue690

Fix local updates from dashboard status dialog actions.