Updates to problem location for opaque keys
Remove package_id and remove lower_ stuff from migrator
STUD-1603
Merge pull request #3842 from edx/ahodges/documentation/LMS2748

Updates to problem location for opaque keys
Merge pull request #3745 from edx/dhm/no-package-id

Dhm/no package
Merge pull request #3899 from edx/opaque-keys

Opaque keys
i18n of Image Response [BLD-723]