Initial version of network information plugin

WIP 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).

The netinfo API doesn't work on the simulator and I had a hard time testing this on my peak device. Curious to know if there are better ways to unit test this. Will look around to see what other plugins are doing.

Sharing my progress to get some feedback and get the discussion going. Will try to get at least a sample app working to manually test, although I can only get wifi on my device.