Allow traffic_ctl to modify records.yaml.

[brbzull0]

The idea would be to use traffic_ctl config set to modify the records.yaml. This will insert or change the existing field in the records.yaml.

If we want to append the new field at the bottom of the document, then we should also change the TS records.yaml loading process, I guess this will not be much different as we had before with records.config which a later line will overlap the previous one, we should probably have this two