Updated docs to be more clear about the different uses of the receive_buffer_size/send_buffer_size in the URI string vs in the attribute of the connector per https://issues.apache.org/jira/browse/APLO-304

git-svn-id: https://svn.apache.org/repos/asf/activemq/activemq-apollo/trunk@1452177 13f79535-47bb-0310-9956-ffa450edef68