Poll for network availability when app is in the background

[ghost]

There's a possible err condition where the user installs the app but first opens it when they have no signal.

In that case, their registration attempt will fail and no device_id will make it to our servers. Given there's no other content to bring them back to the app, we won't get another shot at re-registration.

So, possible solution:

• monitor network connectivity while app is in the background
• when connected, if no registration success, then attempt to re-register

This needs a chunk of research re. how cordova could notify the app on network conditions and is edge-case, so pending for now.

[mfb]

There's now other content in the app so we might be able to close this one.

Hopefully, releasing new versions could also encourage users to come back to the app...