New stanza that retrieves all replies of a post.
Add cascading delete to make node deletion much easier
Better SQL upgrade description
Use timezones in PostgreSQL
Better time and timezones handling

Use moment.js instead of isodate.
Sort in the DB, not in JS
RetrieveReplies: newest items first

Most queries reretrieve new items first; do the same for replies.
RetrieveReplies: use items IDs for RSM
Add test for RetrieveReplies operation
RetrieveReplies: fail when the post is missing
Merge branch 'feature/item-replies' into develop
Merge remote-tracking branch 'upstream/develop' into develop