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
Accumulator refactor:

Stores a single copy of each request from different sources.
Firewalls identical requests.
Implements time based eviction policy.
Tests.
Merge branch 'next' into MAID-563_accumulator_update

Conflicts:
	src/maidsafe/vault/tests/accumulator_test.cc
Merge pull request #91 from benjaminbollen/MAID-554_CreateMaidAccount

Maid 554 create maid account
Linux fix, added request lifetime to Parameters.
Linux fix.
Minor change.
Merge remote-tracking branch 'upstream/next' into MAID-563_accumulator_update
Style fix, tidyup and new test.
Further tidyup.
Updated in line with comments.
Merge pull request #92 from BSMaidSafe/MAID-563_accumulator_update

Accumulator refactor:
Iterates Accumulator's pending request list once to add requests, report current number accumulated and remove expired requests.
Merge pull request #93 from BSMaidSafe/MAID-587_improve_accumulator_efficiency

Iterates Accumulator's pending request list once to add requests, report...
make testing code comply with the changs in DataManager
correct DataManagerDatabaseTest.BEH_GetTransferInfo test
Merge pull request #95 from maqi/MAID-582_passing_DataManagerDatabase_tests

MAID-582_passing_DataManagerDatabase_tests