MB-10252 Add the descriptions of memory-related stats to stats doc
MB-10252 Add the descriptions of memory-related stats to stats doc

Change-Id: Ib0039cc6526eed54c32fb87c8584f8ac7e82c620
Reviewed-on: http://review.couchbase.org/39108
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

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