Added panning by arrow keys feature.
Primary Instances visibility toggled by clicking on a node. (not perfect yet)
Added additional cytoscape classes to instance vertices for convenient selection
Altered the working of instance showup on clicking on instance acc. to make use of new cytoscape classes for instances.
Selecting a node and pressing the character 's', pops up all the secondary instances correspoding to that node.
All the other instances are hidden
Pressing the character 'h' hides all visible instances.