wrap all the extras to permit both ES6 import and use in browser

• taken initially from the existing one that require()s from
  smooth-plotter and synchroniser, for obtaining the Dygraph
  “global” in a module system
• some ways to import put it as .default though so use that
  if .NAME is absent but .default is defined
• apply this to all extras, fixing (#848) (#989) (#1009)
• drop redundant closure where applicable, suitably label otherwise
• label all functions here