Add remote IMAP search support.

* rbayer/IMAPsearch: (21 commits)
  More cleanup
  Code Cleanup getRemoteSearchFullText -> isRemoteSearchFullText line wraps for preference items
  Refactor to allow fetching of extra search results beyond original request.  Most code moved out of ImapStore and ImapFolder and into MessagingController.searchRemoteMessagesSynchronous.  Should make it easier to add remoteSearch for other server types.
  Prevent delete of search results while search results open
  remove duplicated code block
  Don't hide Crypto when IMAPsearch disabled
  Code Style Cleanup: Tabs -> 4 spaces Remove trailing whitespace from blank lines
  tabs -> spaces (my bad...)
  Fix opening of folders to be Read-Write when necessary, even if they were previously opened Read-Only.
  add missing file
  Working IMAP search, with passable UI.
  UI improvements
  Simple help info when enabling Remote Search
  Dependency for preferences
  Basic IMAP search working