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
Financial Aid Application Status and Messages

* #139 Email on submission
* #140 View application status
* #151 Attach messages to application
Reformat some lines that were too long
Merge pull request #153 from caktus/feature/lines-too-long

Reformat some lines that were too long
resolve conflicts
Merge branch 'feature/139-email-finaid-submission' into develop
Stop showing "Add a new proposal" button when it's time

The code would already prevent you from actually submitting a
proposal if no proposal sections were open. This change stops
displaying the button.
Set open period for financial aid applications in the database

Instead of a setting, control the open period for financial aid
applications using the database.

This is mainly because we want to be able to enable applications
on staging for testing without enabling them in production, though
it also means pycon organizers can control the period more easily.
Financial aid application cleanup

* Add hotel arrival and departure dates
* Put verbose names on every field (for translation)
* Style the button for submitting an application message correctly
* Update the tests
Merge branch 'feature/finaid-application-cleanup' into staging

Going ahead and using these changes provisionally on staging (but
won't merge to develop until reviewed).