Collection: default search param values

[tpluscode]

It should be possible to set default value for search template params, similar to sh:defaultValue, so that when a parameter is not provided in the query by a client, the filter will be applied nonetheless

<collection>  hydra:search
    [
      rdfs:label "Search" ;
      hydra:template "{?onlyClosed}" ;
      hydra:variableRepresentation hydra:ExplicitRepresentation ;
      hydra:mapping
        [
          a hydra:IriTemplateMapping ;
          hydra:variable "onlyClosed" ;
          hydra:property </api/bus#unmatched> ;
+         query:defaultValue true ;
          query:filter
            [
              a code:EcmaScript ;
              code:link <node:@pks/filter#onlyClosed> ;
            ] ;
        ] ;