Take advantage of background mode in iOS

[yaronyg]

See here there are serious issues with iOS, JXcore and LibUV when an application gets suspended.

For the moment we are going to deal with these issues by killing all of our ports and servers whenever we get a pause event. But the cost for this approach is that we could have had an extra 2-3 minutes of run time after the user has put us into the background to continue synching data (note that this would only apply to in-process sync's, we can't establish new network connections in the background). For simplicity sake we are going to give up those 2-3 minutes for now but it would be nice to get them back.