No `/mode` topic or service

[jacobwaller]

Wanted to add this myself for a project I'm working on, but do not have time at the moment.

There is no /mode topic or service. Or really, no way to set the current mode of the create at any given time.

[jacobperron]

Exposing this as a service sounds reasonable to me. I'm happy to review a PR adding this if you find time at some point.

[jacobperron]

Duplicate: #13