[model, serializer, test] Conference: +{isOpen, description}
[model] Conference: +{isPublished, description}
adminConference: make isPublished, description observable
adminConference: add isPublished to the editable fields
adminConference: make description an editable field
[views] conference: Add conference description
[views] template:Nav: only show Abstracts if conf.isPublished
Merge pull request #100 from gicmo/confChanges

Changes to Conference (+{isPublished, description}); Show Abstracts nag link only when conf.isPublished