Sexy boxes drag and drop

The plan edit page is modified to show the flavors with a visualisation
of the nodes. Roles can be dragged and dropped on the flavors.

TODO: actually save the flavor for a role in the form
TODO: add a popup for adding the roles to flavors

Change-Id: I9b97f39e3800b5b6c2e5639fcfd186b4196d0190
Merge "Sexy boxes drag and drop"