-addusr
template: ster?clnt=<name|pass>&com=addusr&usr=<usr>&<str_1>=<deg_1>&<str_2>=...
          Order of query params is not important. User name
          must not be empty string.
descript: assigns stereotypes to a user with an associated degree.
          Degree is numeric (double), and expresses relevence.
          For the 'degree' parameters in query string that cannot
          be converted to numeric, NULLs will be inserted in DB.
          The stereotypes must already exist in the DB. If a
          stereotype in the query string does not already exists
          in the DB, or if a (usr, str) pair already exists, then
          code 401 (request error) will be returned. If the error
          code 401 is returned then no records have been inserted
          in the DB.
example : ster?clnt=name|pass&com=addusr&usr=kostas&visitor=0.78&expert=0.9
          ster?clnt=name|pass&com=addusr&usr=0.34&visitor=&expert=0.5
returns : 200 OK, 401 (fail, request error), 501 (fail, server error)
200 OK  : no response body exists.