[WIP] Assessment

This adds applications and reviews.  Huzzah.

Still needs a few things:
- Tests do not cover applications with evidence or reviews with reviewItems.  This is due to FormData not working with arrays.  There may well be an easy solution to this, but I haven't really looked into this yet (I have tested manually and adding and updating these arrays does work)
- Deletion of applications and reviews (and badges, in fact) does not handle deleting the accompanying evidence, reviewItems, and criteria.  Oops.  Going to add delete methods to the Application, Badge and Review models to handle this.
- Doc updates
- The webhooks used by applications may not be the right implementation (at the very least, they are totally unsecure right now).  Need to discuss how these will actually work, and if they will be on an application-by-application basic (as with aestimia), or if they should just use system-level webhooks.