Only move selected convos if from same account

* Add accountUri column to Conversation
* Also add IS_VIRTUAL capability to Folder (for combined folders)
* Check that all conversations to be moved/relabeled from a virtual
  folder are from the same account

Bug: 6280990

Change-Id: Idfc5b3017b16a9f8c1ae5063ba22c66f89d8ca4f
5 files changed