Contributed by Karlyn Benson / Every month, it seems there is one day when there are so many openings and events in the Hudson Valley that it is physically impossible to attend them all. For upstate art lovers, this challenging experience is happening twice, on both Saturday, April 4 and Saturday, April 11. The first Saturday in April brings new exhibitions at SEPTEMBER, Philip Douglas Fine Art, Front Room Gallery, Jane Street Art Center, Headstone…