common

This commit adds a new service API to handle the deliver request to
obtain filtered blocks while still leveraging existing implementation of
the deliver service which was initially introduced inside
AtomicBroadcast RPC service. This commit takes care to preserve clear
separation of concerns by abstracting out common deliver logic making it
possible to specify delivery content while concentrating on concrete
implementation.

Change-Id: I93c49c8358ff765d50b4acc717907be2182976dd
Signed-off-by: Artem Barger <bartem@il.ibm.com>