-setattr
template: pers?clnt=<name|pass>&com=setattr&usr=&=&...
          Order of query params is not important: updates of attribute
          values are performed in the order they appear in the request,
          however the changes are of accummulative nature, so the final
          result is the same.
descript: for the specified user, the value for each specified attribute
          is updated to x , where x is the value corresponding
          to that attribute.
          If no matches are found no records will be updated
          (200 OK will still be returned). If the error
          code 401 is returned then no updates have taken place in the DB.
example : pers?clnt=name|pass&com=setattr&usr=kostas&&lang=GR
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/rows.xsl"?>
          <result>
          <row><num_of_rows>number of relevant rows</num_of_rows></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.