Expose Distance Controller frames to ports

[SteveMacenski]

@naiveHobo something addressed partially in #1729 is that we don't have parameterized frames and that can be a problem for multirobot situations.

The getCurrentPose has logical defaults to map / base_link, but we should have those exposed in the BT for the reason above.

Please expose the global and robot frames as input ports with the same map/base_link defaults (using spin as an example). No modifications need to be made to the BT since you can set defaults.