CB-6411 [BlackBerry10] Updates to beep

- Update to embedded wav file to prevent long fade out
- Fix issues when quantity is not a number
- Fix issues when beep called while previous beep still playing
CB-6411 [BlackBerry10] Work around Audio playback issue
CB-6422 [windows8] use cordova/exec/proxy
CB-6460: Update license headers
CB-6452 Updated version and RELEASENOTES.md for release 0.2.7
CB-6452 Incremented plugin version on dev branch.