Summary: Ref T3650. This adds a create transaction, transactions for metadata (title, langauge, view policy), and comments. Editor is used on all create /edit paths.
Test Plan: made some pastes via web and email - yay. edited pastes - yay. verified txns showed up on pastes and in feed correctly.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T3516, T3650
Differential Revision: https://secure.phabricator.com/D6645
