code added for displaying graph for student nodes
Merge branch 'master' of https://github.com/rptiwari/LaitsV3
Minor fixes to charts
minor fixes - given model graph visible now even when student does not add any nodes
Major change to model JSON:  merge extraDescriptions into
givenModelNodes.  Class "model" now has subclasses:
   "model.given" all given model nodes, including extras.
   "model.solution" is all nodes in the given solution.
   "model.student" student nodes.
Updated documentation and various accessor functions to
match new notation.
fixed graph closing error
Merge branch 'master' into author
Merge branch 'master' into author