Add xhtml2pdf requirement
Add fake test template:
Add basic PDF view for billing
Add the billing view to the urls
Added basic test for billing view
Added correct reportlab version for python 2.6
Move transaction and statement creation test helpers into a separate module.
Move statement PDF URL off the root of the billing URL namespace.
Add PDF link to billing statement admin view.
Change link_callback variables to fit with variable naming convention
Created basic HTML invoice
tiny tweak on table markup
Merge branch 'feature/issue-1039-create-basic-billing-statement-pdf-export' into develop