Figure out how to support bluetooth buttons

[thebitguru]

One of the common requests has been to allow overriding the play/pause button that various bluetooth headsets and speakers have. Users are reporting that the button on those devices continue to launch iTunes. Based on my initial research this might be specific to the utilities that the manufacturers supply. I have not had enough time to validate if this is true in all cases. If it is, then a better approach might be to do something like the Vox global listener, which would require a totally different approach to this.

This new global-listener approach might also eliminate the need for patching a system file.

Unfortunately, I likely won't have much time to devote to this in the near future so please let me know if you are willing to take this one. I can provide some guidance and will accept pull request with the final implementation.