Cleanup some perfgraph code

 - Replace some functionality that has been depracated with dygraphs 1.1.0

 - Remove sorting code from perfgraph.js
   - sorting was moved to gengraphs a while ago, I only left it in in case
     something went wrong

 - Remove most references to 'divs' and 'graphInfo' in dygraphs callbacks
    - I think this is responsible for some graphs occasionally not loading
      (that become much more frequent with some upcoming changes.)