Financial aid application model and form

* model for application
* form for creating and editing applications
* web page for ditto, which hides unneeded fields
* setting to control when applications are open
* add links to dashboard to apply or edit application
* tests
* Whole panel conditional on there being something to show
* Review button conditional on user being reviewer
* Other buttons similarly conditional
Fix test
Default to financial aid applications closed

Our partly-implemented code won't start showing up in production
until we arrange to change the settings.
Fix typo in docs
Simplify deciding which finaid parts to show on dashboard
Finaid textareas full width
Cache figuring out if user has submitted a finaid app
Merge branch 'feature/137-financial-aid-models' into develop