separate topic-commands and topics in help output

[RasPhilCo]

WIP/spike do not review or merge

pros:

• shows topic-commands and topics in separate lists to clarify them as separate objects/concepts
• doesn't mess with config.Topics

cons:

• uses topic's help description, ignoring topic-command's help description (topic-command's help description would have to be found/looked up)
• better to handle this in config?

[RasPhilCo]

Superseded and closed via #64