MB-8012 Store time of deletion in expiry field
MB-8012 Store time of deletion in expiry field

Using this timestamp the compactor can purge delete records once they
reach a certain age.

Change-Id: Ib541de9e1a5c14674eaabbea6c03629f9f713870
Reviewed-on: http://review.couchbase.org/27427
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

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