implement option to use 2D grid for simplification + enable parallel kdtree queries
implement option to use 2D grid for simplification + enable parallel kdtree queries

tudelft3d/masbcpp,KevinWiebe/masbcpp,tudelft3d/masbcpp,jeffcoukell/masbcpp,jeffcoukell/masbcpp,KevinWiebe/masbcpp