Update to better support Android Oreo+

[zello-eugene]

The SDK uses Context.startService to start the Zello app service which doesn't always work when the app is not running in the foreground. Context.startForegroundService is more suitable with Zello app 4.101.2+ because starting the service in foreground mode is properly supported by it, but Context.startForegroundService is not safe to use with older releases. Once the Zello app provides a way to identify whether it properly supports Context.startForegroundService (perhaps by adding a meta data tag to it manifest), make use of it.

[zello-eugene]

We chose to forgo implementing of any sorts of checking of the version of the Zello app. v4.101 has been retired a long time ago and most devices should be switched to 5.0+ by now.