add ubuntu platform
CB-5188:
1. Added amazon-fireos platform.
2. Change to use cordova-amazon-fireos as the platform if user agent contains 'cordova-amazon-fireos'
CB-5316 Spell Cordova as a brand unless it's a command or script
Modify Device.platform logic to use amazon-fireos as the platform for Amazon Devices
[ubuntu] use cordova/exec/proxy
added ubuntu support
Merge branch 'cb_5316' of https://github.com/jsoref/cordova-plugin-device into dev
[CB-5565] Updated version and RELEASENOTES.md for release 0.2.5