Abort loading if we are quitting
GnuPG refactoring:

   * Refactor GnuPG verify and decrypt methods so decrypt can also detect
     verified signatures.
   * Make sure message parser has encryption_info and signature_info on
     all parts, whether there we parsed PGP/MIME or not.
   * Refactor PGP/MIME parser to correctly handle signed multiparts and
     evaluate and strip out all PGP/MIME structure before returning.
   * Test to make sure encrypted data gets indexed by search engine