Remove "ADMIN_MEDIA_PREFIX" (deprecated in Django 1.4)

Delete lms/static/admin resources as they are no longer needed
for the admin page as of Django 1.4

Moved two files that were referenced elsewhere:
lms/static/admin/js/jquery.min.js -> lms/static/js/admin/jquery.min.js
lms/static/admin/js/urlify.js -> lms/static/js/admin/urlify.js
Abstract asset methods into own interface class
then impl the read ones as NotImplementedError placeholders on xml modulestore
PLAT-70
fixup! Remove "ADMIN_MEDIA_PREFIX" (deprecated in Django 1.4)
Remove more pep8 violations
Merge pull request #5828 from edx/sarina/moar-pep8

Remove more pep8 violations
Merge pull request #5800 from edx/dhm/xml_assetstore

Abstract asset methods into own interface class
Merge pull request #5821 from edx/sarina/remove-old-admin-files

Remove admin files deprecated in Django 1.4