Allow db tags to be used

The Mongo driver will then be able to choose the best
host based on tag values, e.g. that in the same
data centre.
Merge pull request #572 from atlasapi/mongo-tags

Allow db tags to be used
Replacing deprecated Rovi publishers for equivalence
PMLSD: Ingest clip images

These have a different form to content images, so weren't
being ingested previously because
Merge pull request #573 from atlasapi/pmlsd-clip-images

PMLSD: Ingest clip images
Merge pull request #575 from atlasapi/rovi-equivalate-en-publisher

Replacing deprecated Rovi publishers for equivalence
Beginnings of change
Taking into account categories for an equivalence task