add ubuntu platform
CB-5188:
1. Added amazon-fireos platform
2. Change to use amazon-fireos as a platform is the user agent string contains 'cordova-amazon-fireos'
[ubuntu] change location of persistent dir
CB-4816 Fix file creation outside sandbox for BB10
CB-5405: Update JS code to use URLs exclusively
CB-5406: Update iOS native code to use filesystem URLs internally
CB-5408: Add handler for filesystem:// urls
CB-5406: Factor out filesystem providers in iOS
CB-5406: Split iOS file plugin into modules
CB-5403: Bump File plugin major version
CB-5406: Extend public API for dependent plugins

The FileTransfer and Media Capture plugins depend on
internals of File; new methods have been exposed for the benefit of
FileTransfer, and old methods restored for Media Capture.
[ubuntu] use cordova/exec/proxy
CB-5118 [BlackBerry10] Add check for undefined error handler
Merge branch 'dev' of github.com:archananaik/cordova-plugin-file into dev
added ubuntu support
CB-5531 WP8. File Api readAsText incorrectly handles position args
Merge branch 'CB-5531' of https://github.com/sgrebnov/cordova-plugin-file into dev
Merge branch 'CB-5532' of https://github.com/sgrebnov/cordova-plugin-file into dev
Partial fix for iOS File compatibility with previous fileTransfer plugin