Initial commit donation module
Check donation module when filtering line item types for extra costs

We were doing this for the Stripe module, but now that the donation module
also exists, we have to check if it is being used also.
Adjust default link_title for donation module
Use separate setting tag for donation module

People might be confused by needing the "stripe_settings" Tag if they
aren't using Stripe.

Also, removes the "offer_donation" setting; if you're using this module,
it wouldn't make sense to have offer_donation = False.
Add line_item_type() method to DonationModule
Update students() and studentDesc() in DonationModule
Change deadline for donations to /ExtraCosts

We could make a separate deadline if this isn't sufficient.
Take out some unused code in donation module
Fix typo causing donation choice to be 'stuck'
Hide donation choices until user checks the box
Tweak text in donation module template
Fix copyright comment in donationmodule.py
Specify program when fetching/creating donation line item type

The lack of a program was causing an error if this function was creating
the line item type (instead of just fetching it).  The program and text
are the only required fields on LineItemType; we don't need to specify an
amount_dec since the user has to explicitly choose the amount.
Donation Module:

Resolved errors causing module to fail
Code cleanup
Fix docstring on DonationModule.isCompleted()
Remove <form> action/method from donation template

The user's selections are handled via Ajax, so the form is never actually
submitted.
Change set_donation_amount JSON view to use POST instead of GET
Merge donation-module-codecleanup into donation-module
Removed checkbox
Removed unneeded key invoice_prefix from donation_settings