marc export mappings and tests
fixes for breaking tests
resolve merge conflicts
update yard requirements
Default extent_type translation to be the enumeration value if no i18n entry exists
Added MediumBlob for longer notes
When doing an import, retry the import on an optimistic locking error
Merge pull request #571 from hudmol/MARC-export-final

marc export mappings and tests
Merge pull request #572 from hudmol/blocker-fixes

Unblockers!
Merge branch 'master' into coveralls-master