Latex fixes

Less controversial changes:

* 6dd6de6677 (batch mode flags) prevents LaTeX from dropping to a prompt when you're running manage.py test or manage.py runserver from an interactive shell.
* add786e397 (landscape options) renders landscape-oriented student schedules on landscape-oriented paper, rather than cut-off on portrait-oriented paper. (Fix requested by Chicago.)

More controversial changes:

* 28955c82a2 (subprocess.check_call) stops rendering of LaTeX as soon as an error is encountered. Possibly-unwanted side effect is that PDF catalogs fail to render upon any LaTeX error.
* f49391f5c4 (texescape on '\n') prevents generating lots of `! LaTeX Error: There's no line here to end.` Possibly-unwanted side effect is that several newlines in a row in source produces several newlines in a row in output, rather than just a paragraph break.
* 8c3c58c1a6 (completion certificates) puts class descriptions back into completion certificates. People may have already gotten used to them not being there.