Fixes based on comments in PR.

These comments will be squashed.

CDTPushReplication.m
  * _docId set in -init

CDTReplicatorFactory.h
  * Class description comment was updated.

CDTReplicationFactory.m
  * line-length violation fixed.

DatastoreCrud.m
  * Error comment slightly improved.

CDTReplicationTests.m
  * Code cleanup -testCreatePushReplicationWithFilter. Line-length
fixes and error comment changes.

ReplicationAcceptance.m
  * unnecessary tests removed from -pushToRemoteWithFilter.
  * unnecessary checks for nil on filter/filterName and params removed
from -pushToRemoteWithFilter and -pullToRemoteWithFilter