require Source.status='enabled' to publish
#214 UI redesign: drop publish signup from front page, rearrange rest
 #214 UI redesign: refactor user template into an inheritance hierarchy
refactor publish_test: add assert_success()
publish: allow summary and name as well as content. for #219
finish #214 UI redesign, notably doing webmention discovery on all sources
update tests for #214 and 7cbc07ae2472c6cb9983b599cf8a14ab6f91b57e