Update MongoDB version to 2.5.4 development (in advance of 2.6 release)
Set replica set as config key on server member
Rename MongoClientSupport MongoDBClientSupport for consistency with other classes
ReplicaSetConfig sets number of votes on members

Allows a replica set to be resized to up to twelve members and to have
up to seven voting members (the maximums permitted by MongoDB).
MongoDB: Ensure primary gets a vote and there are an odd number of voters
MongoDB: Address review comments

* Removed REPLICA_SET_ENABLED config in favour of isReplicaSetMember()
* Null checks and other miscellaneous fixes
Replace getClient on MongoDBServer interface with replica set methods
Mark MongoDBClientSupport Closeable
Merge pull request #1125 from sjcorbett/feature/mongodb-membership

Up to twelve members of MongoDB replica sets