add no-op GMaven plugin (closes #278)
add no-op GMaven plugin (closes #278)

tajinder-txstate/lenskit,vaibhav345/lenskit,vijayvani/Lenskit,amaliujia/lenskit,kluver/lenskit,martinlaz/lenskit,chrysalag/lenskit,chrysalag/lenskit,binweiwu/lenskit,kluver/lenskit,kluver/lenskit,amaliujia/lenskit,blankazucenalg/lenskit,aglne/lenskit,aglne/lenskit,kluver/lenskit,martinlaz/lenskit,kluver/lenskit,binweiwu/lenskit,linjunleo/lenskit,blankazucenalg/lenskit,tajinder-txstate/lenskit,vaibhav345/lenskit,vaibhav345/lenskit,vaibhav345/lenskit,tajinder-txstate/lenskit,linjunleo/lenskit,tajinder-txstate/lenskit,vijayvani/Lenskit