Bug 934230 - [v1.2] Update all manifest files to be in line with master
Merge pull request #13332 from bobsilverberg/v1.2manifest

Bug 934230 - [v1.2] Update all manifest files to be in line with master
Bug 911944 - Handle message actions and increase test coverage r=julienw

- Added parsing message actions in SI and SL messages
- Implemented specific behavior for actions such as delete and signal-none
- Fixed a minor issue when doing age-based message replacement
- Added unit-tests for the new functionality
- Added unit-tests coverage to the MessageDB object