-getdrt
template: pers?clnt=<name|pass>&com=getdrt[&grp=<ftr_group_1>&grp=...]
          Order of query params is not important. Feature group
          is a template path expression 'pathname', representing
          all features with name starting with 'pathname'. The
          'grp' query parameters are optional.
descript: selects the corresponding decay rates for the specified
          feature groups and formats an XML answer with the group
          names and rates. If the specified groups do not exist
          in DB, the result will not have any row elements (200
          OK will still be returned). If no 'grp' query parameters
          exist in the request, all the feature groups and decay
          rates in the DB are selected. The results are sorted
          according to descenting decay rate (1->0).
example : pers?clnt=name|pass&com=getdrt&grp=page10.banners&grp=frequency.allfeatures
          pers?clnt=name|pass&com=getdrt   (selects all group, rate pairs in DB)
returns : 200 OK, 401 (fail, request error), 501 (fail, server error)
200 OK  : in this case the response body is as follows
          <?xml version="1.0"?>
          <?xml-stylesheet type="text/xsl" href="/resp_xsl/decay_groups.xsl"?>
          <result>
              <row><grp>feature group</grp><rate>decay rate</rate></row>
              ...
          </result>
comments: the reference to the xsl file allows to view results
          in a web browser. In case the response body is handled
          directly by an application and not by a browser, this
          reference to xsl can be ignored.