Update to django_polymorphic 0.4.2.
Remove unused DocDataWebMenu model.

Having it as an empty model didn't work with Django Polymorphic.

BB-191 #resolve
Voucher landing page styled
WIP: Voucher Landing Page
Merge pull request #296 from prashantpalikhe/voucher

Voucher landing page styled
Merge pull request #294 from benkonrath/payment-fix

Payment fix