Modularize Repository transactions

Summary: Depends on D19828. Ref T13216. Before adding new transactions to repositories (filesize limit, copy time limit, etc) modularize the existing transactions.

Test Plan:

• Created repository.
• Edited callsign (invalid, valid, duplicate, add, remove).
• Edited short name (invaild, valid, duplicate, add, remove).
• Edited description (add, remove).
• Edited encoding (invalid, valid, remove).
• Allowed/denied dangerous changes.
• Allowed/denied enormous chagnes.
• Activated, deactivated, reactivated.
• Changed tags.
• Changed push policy.
• Changed default branch (add, remove).
• Changed track only: add, remove, invalid function, invalid regex.
• Changed autoclose only: add, remove, invalid function, invalid regex.
• Changed publish/notify.
• Changed autoclose.
• Changed staging area (add, remove, invalid).
• Changed blueprints (add, remove).
• Changed symbols (add, remove).
• Grepped for PhabricatorRepositoryTransaction::TYPE_.
• Reviewed transaction history:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13216

Differential Revision: https://secure.phabricator.com/D19829