New search implementation for IMAP in MessagingController

* Add protocolSearchInfo column to Message table; this can be used
  to store information related to search results.  For IMAP, we
  store the serverId of the mailbox that the message lives in on
  the server
* Add upgrade code for this column
* Change MessagingController to use the proper serverId for remote
  operations, depending on whether the Message is a search result
  or not
* Fix some smaller issues with earlier code

Change-Id: I0c7f1d89a4659b95701d02646c0e8426680e2f6a
6 files changed