Addition of reverse map for retracing anmaid and maid message id back to the original message id.  Most conservative solution to MAID-554.
Fixed map iterator by adding missing std::make_pair() for reverse_pending_account_message_id
Replaced reverse_dictionary with XOR reversible function for message_id generation.
Merge branch 'next' into MAID-554_CreateMaidAccount
Merge pull request #91 from benjaminbollen/MAID-554_CreateMaidAccount

Maid 554 create maid account
Merge remote-tracking branch 'upstream/next' into MAID-563_accumulator_update
Style fix, tidyup and new test.