Initial version of firefox os network information plugin

Supporting both the [old network info API](http://www.w3.org/TR/netinfo-api/) and [the new one](http://w3c.github.io/netinfo/). FirefoxOS has recently moved to the new one see [bug 960426](https://bugzilla.mozilla.org/show_bug.cgi?id=960426).

Tested using a fxos nightly build on a device.