Add replication section to serverStats.metrics

"repl" : {

	"apply" : { //applied operations on the replica (not primary)

		"batches" : {

			"num" : ##, //number of batches applied across all db active in the batch

			"totalMillis" : ## //time to apply

		},

		"ops" : ## //applied operations

	},

	"buffer" : { //stuff to be applied, came off the network and in a holding pattern till the application threads start to work on it.

		"count" : ##, //current count items in the buffer 

		"maxSizeBytes" : ##, //max size of the buffer, in bytes

		"sizeBytes" : ## //current size of the buffer, in bytes

	},

	"network" : { //network stats during replication from the source

		"bytes" : ##, //the amount of data read from the replication source

		"getmores" : {

			"num" : ##, //number of getmore (batches) made to the source

			"totalMillis" : ## //time taken to collect the data

		},

		"ops" : ##, //number of ops read from the source oplog

		"readersCreated" : ## //number of oplog readers created -- this will happen if any error occurs on the connection (timeout, network loss, etc), if a new source is used for example

	},

	"oplog" : {

		"insert" : {

			"num" : ##, //entries inserted into the oplog

			"totalMillis" : ## //time take to do the inserts

		},

		"insertBytes" : ## //the size (in bytes) that were inserted

	},

	"preload" : { //these number depend on the prefetch mode

		"docs" : {

			"num" : ##, //documents which were loaded before being updated

			"totalMillis" : ## //time taken to load the docs

		},

		"indexes" : {

			"num" : ##, //number of index entries loaded before updating the docuemtnes

			"totalMillis" : ## //time taken to load the index entries

		}

	}

}