WIP mediacore
refactor mediacore into its own module and add rest endpoint
publish media and sign embed url
fix log name
allow express to accept POSTs up to the limit we set in nginx
remove unused video thumbnail sizes
external previews
store mediacoreId to content revision mapping
add callback endpoint for mediacore thumbnails
use more appropriate mediacore thumbnail sizes
(MediaCore Review) Review followup, unit tests, added support for audio
Merge branch 'master' into mediacore
(MediaCore Review) Self-review. Lock down global admin config for mediacore items for now
(MediaCore Review) Use revision data instead of content data for upload file
(MediaCore Review) Self-review, intermittent test failure fix
Merge branch 'master' into mediacore

Conflicts:
	node_modules/oae-content/lib/api.js
	node_modules/oae-content/lib/constants.js
	node_modules/oae-tests/lib/util.js
(MediaCore Followup) Review followup
Merge remote-tracking branch 'origin/master' into mediacore
(MediaCore Followup) Use new tenantRouter for binding mediacore routes
Merge pull request #679 from mrvisser/mediacore

Mediacore Integration Followup