runctl: add npm ls-like package listing

Since it's supported by the runctl control channel, the same package
information will be available to the process manager/controller UI when
ready.

I'll add a test, but this is a light wrapper around strongloop/strong-npm-ls#1
true, you have to read to the end to see that rsp can be cleared if you don't want the auto-response, I can see how that's not so clear, expecially when looking at just a diff. I might change later, would like to leave for now.