Support work sources
Merge pull request #48 from commonsmachinery/core-sources

Support work sources
Better idToObject conversion for work.collabs.user, work.annotations.updated_by and work.media
Work.collabs.users: events and access
Minor fixes.
Expand source work into id/href pair (fixes #52)
Better idToObject conversion for work.collabs.user, work.annotations.updated_by and work.media
Add missing properties for source objects (fixes #51)
Accept user objects for work.collabs.users
Require write to remove media from work
error message handling
update gravatar hash, Fixes #49
lint
jshint fixes
Merge pull request #56 from commonsmachinery/minor-issues

Minor fixes.
Merge branch 'master' into work-collaborators

Conflicts:
	frontend/lib/api/respond.js
Merge branch 'work-collaborators'
Cleanup after previous merge
list annotations
media and annoations (simple list)