Add functionality for creating custom graphs

[HKH515]

Allow the user to create/delete vertices/edges

[rostam]

This functionality is there. I have some suggestions.
Whenever that user adds a vertex or edge, the whole graph is built again:
cy.batch(function(){
cy.elements().remove();
cy.add(nodes);
cy.add(edges);
applyLayout();
});
setTimeout(reload, 1000);

Why do you that. Why not just adding that specific new element?
cy.add(...)

Is there any problem with that?

[HKH515]

We were having some problems where some nodes that we added in cyto didnt exist in the backend, so we just resorted to get all info about the graph each time we edit the graph clientside, it's not very efficient but this was a solution that fixed that bug. To be honest we are not very proficient with cytoscape, we don't really know how to to this efficiently in cytoscape.