unit: check creation of document replicator (#2388)
unit: check creation of document replicator (#2388)

* creation of CBLDocumentReplicator and CBLReplicatedDocument.
couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios