Initial download working
No more twig

Stopped trying to use twig for downloading because I couldn't leave any
whitespace, making it unreadable. Switched to echoing from the
controller. Giving me a lot more power to do calculations and minimize
errors.
Better downloading,

Should be able to handle people not finishing, people dropping the
class. Also got stopped storing unencrypted student ids anywhere.
Downloading overhaul
Grade Entity

Added an entity to represent a graders grade for an answer.
Bug fixes, bio:setup

Added code to initialize the examglobal entity in the database.

Fixed bugs:
1. The loops that found the total mean score would overwrite variables,
causing the points to be displayed incorrectly.
2. If the exam didn't exist it would try to continue anyways
3. If you had been assigned a grader who didn't grade, it would try to
add the null scores anyways.
4.The average loop didn't even compute the average…
Merge branch 'download-exam' into global-settings