On OS X, copy Rhythm-related files to the application bundle's Resources folder, and use the bundled copies at run time

- Also, changed Clock divider level: label to Clock divide ratio:
- Also, clock divide settings are now serialized to the configuration
  XML during a settings save.

- Sync signal, wired to BNC out with the update rhd2000.bit, can be set
  to a multiple of the sample clk period using the RHD2000Editor
- This commit corresponds to this pull request:
  https://github.com/open-ephys/rhythm/pull/11