CB-5611 firefoxos: battery-status plugin
Updated documentation. Added support for mozBattery.
CB-4519, CB-4520 low+critical weren't firing when level went from 21->19, and were when level went 19->20
Merge branch 'initial' of github.com:mozilla-cordova/cordova-plugin-battery-status
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/cordova-plugin-battery-status