Apply cssClass to edgePaths from a node in class diagrams

[akulmehta]

When using a class diagram we can style the node using cssClass. However, sometimes you also want to add styles to the relationship / links of the nodes. It would be nice to have the ability to add the css classes to the relationship arrows/links as well.

An example use case which I faced was where I am trying to hide certain nodes and relationships in some figures while showing them in another using reduced opacity. Alternatively, one could highlight certain nodes and relationships with colors.

There should also be a way to assign ids to the relationships.