Examples/Getting started: clean up ns call.
Adopt overtone.live's namespace immigration

- add api.clj like overtone.api
- remove unnecessary namespaces from core
- dsp;genetic/utils: fix namespace clash with overtone.time
- editor:
  - use in-ns instead of explicit ns creation
  - clean up namespace
  - use directory of active tab as starting point on open/save
  - add more examples to menu