mention email is supported in addusertogroup/removeuserfromgroup management commands
refactor iarc code, add missing descs (bug 1035408)
Merge pull request #2290 from ngokevin/iarcrefactor

refactor iarc code, add missing descs (bug 1035408)
fix iarc cron
fix iarc backwards-compat es index
Merge pull request #2301 from cvan/mention-email

mention email is supported in addusertogroup/removeuserfromgroup management commands
feed item indexer
feed es view, es feed item serializer
update feed api docs
index all feed elements (app/brand/coll/shelf) fully
deserialize apps from es in feed view
layer in ES serializers for feed
sprinkle some test work