SERVER-11995 Have authSchemaUpgrade sent to a mongos upgrade auth schema everywhere.

In particular, sends the commands to each shard, as well as performing the upgrade on the
config servers.

Also, allow user to specify maximum number of upgrade steps to take on any given shard.
Defaults to "as many as necessary".

To achieve these changes, separate implementations of the upgrade command are provided to
mongos and mognod.
SERVER-11995 Test of successful upgrade of auth schema on a sharded cluster w/ rs shards.
Remove a stray stringstream in QueryPlannerAccess
SERVER-1205 explode point interval scans to obtain sort