Fix enrich_date to handle dates < 1900 (#7562)
Refactor to-dpla modules into mapper classes
Added test for pre-1900 dates in enrich_date (#7562)
Fixed problems with pipeline lacking "/" character (#7565)

Add initialization of saved_colls to poll_storage.main().
Ensure forward slash exists in URI path in enrich.pipe().
Temporarily disabled MWDL fetcher test
Fix for 6919

- Added set_context module and updated item and collection
  enrichment pipelines for all profiles
Added Getty Research Institute set to IA profile (#7539)
Bumped version to 27.1
Merge branch 'release-v27.1' into develop
Improved exception handling in couch module (#7486)

The return values of all of these functions should be changed, and
errors should be indicated by exception classes in the couch module.
The return codes are not system exit values and they don't have
anything to do with array or string indices, so they should not be
0 for success, -1 for failure.

With errors indicated by exceptions, we could more conveniently pass
richer information about the error, which could then more easily be
inserted into the dashboard document.  This will be more important down
the line when we're talking about further automating the ingestions,
since we'll need errors to be reported through a web interface that has
access to the dashboard document.
Bumped version to 28.0
Merge branch 'release-v28.0' into develop
Fixes for errors noticed in Mark B's review of *-to-dpla refactor
Updated export file structure (#7540)

Updated the structure per:
https://digitalpubliclibraryofamerica.atlassian.net/wiki/display/TECH/Database+export+files
Bumped version to 28.1
Merge branch 'release-v28.1' into develop
Fixed exceptions in mapper modules (#7581)

Added missing imports, fixed other issues in  marc_mapper,
hathi_mapper, and uiuc_marc_mapper.

Note that the keyErrorAsNone parameter is now passed as True to
getprop() in MARCMapper._get_mapped_value(), which should result
in an empty list if the property doesn't exists, which seemed fine
because that's a condition that's already handled in the next
statement in that function.
Fixes to mapper classes (#7589)

- Fixed imports in mapper classes
- Fixed getprop() calls
Bumped version to 29.0
Merge branch 'release-29.0' into develop