Fix issues with Interactive Timescale

[nicholascar]

• Middle Pleistocene is 781 ka in the interactive chart (updated to 774 ka in the pdf version)
• Beginning and End links for each interval go to the Stratotypes directly, and not to the Boundaries first
  • For example, select ‘Messinian’ and then browse through the beginning and end and you go to the resources BaseMessinianSP and BasePlioceneSP.
  • OTOH on the source data at ARDC when you start at http://resource.geosciml.org/classifier/ics/ischart/Messinian the beginning and end go to http://resource.geosciml.org/classifier/ics/ischart/BaseMessinian and http://resource.geosciml.org/classifier/ics/ischart/BasePliocene first, with separate links then to the temporal position and also to the stratotype.