Allow relationships to be set with a Workflow SubAction

[craigWagner99]

As reported in https://dotcms.zendesk.com/agent/tickets/104583 Reproducible in dotCMS 5.3.8.5

Relationships are currently able to be set with the API or a content import but they are not able to be set with a workflow action.

Describe the solution you'd like A new workflow subaction or the ability to use code in the Velocity Script Actionlet to set a relationship.