allow plugins lacking web_client to add grunt targets, fixes #551.
allow plugins lacking web_client to add grunt targets, fixes #551.

RafaelPalomar/girder,jbeezley/girder,msmolens/girder,Xarthisius/girder,opadron/girder,Kitware/girder,salamb/girder,essamjoubori/girder,chrismattmann/girder,sutartmelson/girder,jcfr/girder,essamjoubori/girder,adsorensen/girder,salamb/girder,msmolens/girder,RafaelPalomar/girder,sutartmelson/girder,jcfr/girder,jcfr/girder,manthey/girder,adsorensen/girder,manthey/girder,jbeezley/girder,opadron/girder,essamjoubori/girder,manthey/girder,Xarthisius/girder,data-exp-lab/girder,RafaelPalomar/girder,girder/girder,chrismattmann/girder,essamjoubori/girder,sutartmelson/girder,jcfr/girder,chrismattmann/girder,msmolens/girder,girder/girder,Xarthisius/girder,chrismattmann/girder,jbeezley/girder,Xarthisius/girder,kotfic/girder,essamjoubori/girder,opadron/girder,msmolens/girder,Kitware/girder,adsorensen/girder,opadron/girder,chrismattmann/girder,opadron/girder,data-exp-lab/girder,jcfr/girder,RafaelPalomar/girder,girder/girder,sutartmelson/girder,kotfic/girder,adsorensen/girder,jbeezley/girder,Kitware/girder,manthey/girder,kotfic/girder,girder/girder,sutartmelson/girder,kotfic/girder,data-exp-lab/girder,kotfic/girder,Kitware/girder,salamb/girder,adsorensen/girder,salamb/girder,RafaelPalomar/girder,Xarthisius/girder,data-exp-lab/girder,msmolens/girder,data-exp-lab/girder,salamb/girder