Added timestamp as a first class citizen in message and Nrv.

Since attachements are node bounds, no migration is required.
Fix idents
Merge branch 'olivier-nrv-timestamp' into manu-message-timestamp
Merge branch 'master' into manu-message-timestamp
Merge branch 'manu-replication-consistency-fix' into manu-message-timestamp
Merge branch 'master' into manu-message-timestamp
Removed Consistency.get/setMessageTimestamp and use Message.timestamp directly
Merge pull request #152 from wajam/manu-message-timestamp

Integration of message timestamp