more granular transactions in grading [LMS-1480]

remove field_data_cache from grades.grade and grades.progress_summary

cleans grading code by adding wrappers
Merge pull request #1655 from edx/adam/more-granular-grading-transactions

Adam/more granular grading transactions
Revert: Allow any part of protocol name to be lowercase or uppercase.
Merge pull request #1659 from edx/hotfix/revert-transcripts-protocol-validation

Revert "Don't allow users to enter video url's in http."
Revert "more granular transactions in grading [LMS-1480]"

This reverts commit 19dd49f35510f9713899534e049edbf1ffe1250a.
Merge pull request #1669 from edx/hotfix/revert_grading_manual_tx

Revert "more granular transactions in grading [LMS-1480]"
Merge branch 'release'

Conflicts:
	cms/djangoapps/contentstore/views/item.py