MB-4987 Add the description of KV Store stats
MB-4987 Add the description of KV Store stats

Conflicts:

	docs/stats.org

Change-Id: I47f79210f5282cd3c32feeb33fd81c34387a8dbf
Reviewed-on: http://review.couchbase.org/14452
Reviewed-by: Michael Wiederhold <a17fed27eaa842282862ff7c1b9c8395a26ac320@couchbase.com>
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

membase/ep-engine,jimwwalker/ep-engine,jimwwalker/ep-engine,abhinavdangeti/ep-engine,owendCB/ep-engine,jimwwalker/ep-engine,daverigby/ep-engine,abhinavdangeti/ep-engine,daverigby/ep-engine,abhinavdangeti/ep-engine,daverigby/ep-engine,couchbase/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,abhinavdangeti/ep-engine,hisundar/ep-engine,teligent-ru/ep-engine,hisundar/ep-engine,teligent-ru/ep-engine,owendCB/ep-engine,sriganes/ep-engine,owendCB/ep-engine,hisundar/ep-engine,sriganes/ep-engine,couchbase/ep-engine,owendCB/ep-engine,daverigby/kv_engine,membase/ep-engine,teligent-ru/ep-engine,hisundar/ep-engine,membase/ep-engine,couchbase/ep-engine,sriganes/ep-engine,daverigby/kv_engine,daverigby/kv_engine,membase/ep-engine,jimwwalker/ep-engine,daverigby/ep-engine,sriganes/ep-engine,abhinavdangeti/ep-engine,daverigby/kv_engine