remove all methods unrelated to documents replication

... from capi_ddoc_replication_srv

Change-Id: I046fbc05d4c6bdd535ece784fabb59cc63510937
ns_couchdb_storage - module that contains storage related functions

... that will be executed on ns_couchdb node

Change-Id: I97f884809ea9550015d0f6874d4b59239a726c69
wip

Change-Id: I9d2de7424a94b404d9fb19c94df5c3a90b4fc8b5