billing template

This has the billing template with bootstrap3 and inheritance.
still needs contexts when rendering.

SUMMARY:
/templates:
  base.html - base for all pages (header, content, and footer blocks)
  system_base.html - base for all modules (extends base.html customizes header to a bootstrap navbar)
  login.html - generic login page with {{cover_url}} and {{system_name}}to change background to adapt to other systems
  stub.html - generic stub for student info display
/templates/billing:
  base.html - extends system_base.html detailed base html for billing
  home.html - billing system home page