simplify ModelView Public API

[#41923323]

Public API for ModelView container now includes just these functions:

  update()
  scale()
  setFocus()
  resize(w, h)
  repaint()
  reset(newModelUrl, newModel)
  model2px(val)
  model2pxInv(val)

I removed:

  processOptions()
  setupDrawables()
  updateMoleculeRadius()
  updateDrawablePosition()

List of replacements for removed functions:

  updateDrawablePosition => update
  setupDrawables         => repaint
  nm2p                   => model2px
  nm2pxInv               => model2pxInv