Create a service for ZeroConf

[rtibbles]

Migrating to chaquopy makes creating and maintaining services for independent parts of the Kolibri application significantly easier.

Creating a separate service for ZeroConf is the starting point for later work to potentially replace ZeroConf in the Android context with Android native peer discovery mechanisms.

It is possible that this work would also require updates on Kolibri, just in case running ZeroConf not from within the KolibriProcessBus would cause issues.

This should be a background service that implements the life cycle hooks of a service: https://developer.android.com/develop/background-work/services#Lifecycle to start the ZeroConf monitoring and stop it appropriately.

This service will be called to start when the app is loaded, but should not block app startup.