Actions CLI - tracer implementation

Just connects the command line 'actions' and 'do' to the apiserver; basic initial CLI implementation
I'm not sure we would or should have got results when the error is not nil -- feels like a bug? Even if it's a deliberate decision, it's non-standard enough that I'd expect something like ErrPartialResults to flag the results' availability.

I'd also generally suggest that one consequence of the multiple-formatters thing is that it's a good idea just to define an output type and set the serialization stuff on there. (Apart from anything else, returning straight results from the API is going to be really nasty when the API changes: (1) that change accidentally becomes a CLI change, and probably a breaking one, when it really shouldn't, and (2) the API types certainly shouldn't have yaml serialization defined on them, and YAMLing them will cause unexpected field names -- and if the json output and the yaml output don't match, we may suffer unpleasant consequences (like mobs with pitchforks).