Adds auto-imports to shell_plus.

This uses django-extensions's SHELL_PLUS_POST_IMPORTS.  It also bumps
the django-extensions version to 1.2.5, since SHELL_PLUS_POST_IMPORTS
only does anything in >=1.2.3.  The only known backwards-incompatibility
is to UUIDField, which we do not use, so this should be safe.
Adds some more imports, and fixes esp.program.modules.models import.
Add UserBitImplication import which was failing
Merge pull request #885 from learning-unlimited/shell-plus-imports

Adds auto-imports to shell_plus.
Merge pull request #891 from btidor/main

Display PDFs and media inline
Fix miniblog 0003 migration bug
Fix program modules 0025 migration bug
Fix user_classes.js

This only alters the size of the "#main" div if it is marked via a
CSS class as resizable.  The main.html templates in the repository
and the generic1 theme are given this class.

Fixes #875.
Merge pull request #876 from learning-unlimited/deployment-fixes

Deployment fixes
adds batch renewal function to student registrations
Merge pull request #899 from learning-unlimited/add_batch_renew_student_regs

adds batch renewal function to student registrations
Increases LaTeX PNG resolution.

This is used by the schedule printing script.  96 DPI is pretty blurry;
I found empirically that 192 was not too much slower and looked a lot
better.
Merge pull request #902 from learning-unlimited/increase-latex-png-resolution

Increases LaTeX PNG resolution.