Add mustache helper 'using' and apply to 'owner'

* 'using' ensures arguments are fully loaded before rendering content
Load info widget entirely client-side
Fix Section edit and delete
Merge remote-tracking branch 'origin/develop' into feature/additional-fixes
Add References to Section tree
Changes to keep db_migrate path Python 2.6 compatible

* AppEngine supports 2.7, but one deployment environment uses 2.6 still,
  and must run migrations.
Re-enable ordering Events by id
Only show available roles when a user is selected
Merge pull request #249 from reciprocity/feature/additional-fixes

Two fixes, one improvement