Changes for NO_XXX

- Added Message.NO_MESSAGE
- Renamed PSEUDO_ACCOUNT_ID_NONE to NO_ACCOUNT
- Removed PARENT_KEY_NONE and use NO_MAILBOX instead
- For starters, cleaned up the UI controllers to use them.

Change-Id: I6cfd87ece2fced8e9f7c76d034c4d1dbf9e4db10
11 files changed