Approximate date and  return links

Altered views to include approximate date and  HttpRequest.META and altered templates.

Changed the people_view and person_detail template to include approximate date instead of the birth and death year. Updated the model string method to include the approximate birth and death dates and updated the person model test to match the model string method. Fixed the return to previous page links on the person_detail template and the makers_detail template to return the user to the proper link based on the original page the user was viewing. Added url template tags to the return href in both templates. Altered the markerDetailView to include Http_REFERER.