CR-4304 Fix for OPENDJ-1521: Document addrate tool

git-svn-id: https://svn.forgerock.org/opendj/trunk/opendj@10950 41b1ffd8-f28e-4786-ab96-9950f0a78031
CR-4307 Fix for OPENDJ-1525: Document new maxDuration and warmUpDuration options for xxxrate tools

git-svn-id: https://svn.forgerock.org/opendj/trunk/opendj@10961 41b1ffd8-f28e-4786-ab96-9950f0a78031