Add additional documentation on plugin tests
Add additional documentation on plugin tests

Xarthisius/girder,data-exp-lab/girder,RafaelPalomar/girder,Kitware/girder,Kitware/girder,adsorensen/girder,RafaelPalomar/girder,jbeezley/girder,adsorensen/girder,Xarthisius/girder,jbeezley/girder,kotfic/girder,data-exp-lab/girder,kotfic/girder,manthey/girder,RafaelPalomar/girder,manthey/girder,Kitware/girder,data-exp-lab/girder,manthey/girder,kotfic/girder,RafaelPalomar/girder,jbeezley/girder,Xarthisius/girder,adsorensen/girder,kotfic/girder,Xarthisius/girder,Kitware/girder,RafaelPalomar/girder,Xarthisius/girder,girder/girder,adsorensen/girder,adsorensen/girder,kotfic/girder,jbeezley/girder,girder/girder,manthey/girder,girder/girder,data-exp-lab/girder,girder/girder,data-exp-lab/girder