Enhanced link generation for families.

- Implemented Study:{getLink,trackLinks}
  Everytime Renderer.render is called and updates the fragment as introduced in #29,
  trackLinks is also called with that fragment.
  This way the study knows for each StudyName and PageView that where used,
  what the last setting was, so that these fragments can be used for getLink.
  If no fragment is known, getLink falls back to clear the current settings,
  and only generate a fragment for the choosen family and pageView.
- Fixes #30