Make PM called by controller, passing in the mode.
Start work on changing PM format.
addConnections function in drawmodel.js
Merge branch 'master' of https://github.com/rptiwari/LaitsV3
calculation.js and model.js added with switch functionality for student model and solution model
Change JSON format to have distinct id for given nodes
and student nodes.  Also, there should never be a case where a node id
is changed.  Also, use id to match student and given model
and label description choices.

Simplify if(expr === true) -> if(expr)

Work in progress on huge rewrite to PM.
Change css to have new student node names (needs to be removed).
Fix some typos in example JSON
Move more node creation stuff into addNode so that
Create Node button will open node editor.
Remove modules "node.js" and "student_node.js"
since creating a new node is more naturally a
part of addStudentNode.
Remove extra getters and setters that are not
needed (or are trivial) if node ids never change.
Changes to the json format.
Add "id", "name" and "units" to the extraDescriptions
Name changes:  correctDesc -> description and studentSelections -> selections
Merging changes; added addNode() function to given object.
Merge branch 'master' into megha2

Conflicts:
	www/index.html