Make more abstractions extend to-sc-id - buffer,bus, sample, etc. Busses can now be passed as arguments to trigger and control synths without requiring manual extraction of ids:

(def b (audio-bus))
(ctl foo :out-bus (:id b)) ;=> this used to be the the only approach
(ctl foo :out-bus b)       ;=> now works

* audio-bus and control-bus are now records
* buffer ns use node ns rather than the other way round
* added idify and to-id to match similar fns in overtone.helpers.lib
*