Merge branch 'diana/verified-certs-payment' into ormsbee/verifyuser_func

Conflicts:
	common/djangoapps/course_modes/models.py
	lms/envs/common.py
	lms/envs/dev.py
fix typo in config file
Fix double requirement specification (django-model-utils)
Merge pull request #779 from edx/fix/cdodge/check-xml-attribute-existence

ErrorDescriptors do not have xml_attributes field
Merge pull request #504 from edx/feature/vik/oe-ui

Feature/vik/oe ui
Merge remote-tracking branch 'origin/master' into fix/vik/oe-state
initial commit of shopping cart and cybersource integration
added shopping cart list template, embedded form
add parameterization of cybersource creds
Move shopping cart from session into model/db
add Validation function for cybersource receipt POST
add Order model fields for receipt generation
factor out cybersource processor from cart
Lots more verification of CyberSource reply + receipt generation
about page changes, refactor processor reply handling
Add in new VerifiedCertificate order item
Pull CyberSource values from environment variables
when in a dev environment.
Remove enrollment_cost from course_module
Some cleanup fixes to get verified certs working.
Put shopping cart views behind flags