Towards supporting transporters as workcells

[Yadunund]

Based on insights from #42, this is a meta-ticket to track features needed to treat transports as workcells

• Standard definition for task.type that correspond to transportation tasks
• Standard notation for describing pickup/dropoff parameters at each destination
• RMF integration does not yet support parallel work orders #64
• Refactor Workcell Bidding + Assignments into respective BT nodes #66

[aaronchongth]

Closing this as we are moving towards dedicated transporters.