Move low-level kvstore operations into a separate lib.
Move low-level kvstore operations into a separate lib.

This allows for reuse across components.

Change-Id: I5a0cdbefadf91e33473f5a3b27b28de3d115e72c
Reviewed-on: http://review.membase.org/4277
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

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