Setting selector types

Selectors now have to be created either like this:

{
  type: 'FragmentSelector',
  conformsTo: 'http://www.w3.org/TR/media-frags/'
  value: YOUR_SELECTOR_VALUE
}

or the new SVG version:

{
  type: 'SvgSelector',
  value: YOUR_SELECTOR_VALUE  // <-- inline SVG code like '<svg>...</svg>'
}