Actions CLI - tracer implementation

Just connects the command line 'actions' and 'do' to the apiserver; basic initial CLI implementation
And I think it's "target" not "unit" -- and I'd hope that we'd be able to use `do foo <service>` to mean either "run the service action foo" or "run the unit action foo on every unit", and the second meaning should be trivially supportable with what we're doing right now: no service actions necessary.