Parent display name in location metadata

For a future PR (not here)... We should do something about these method signatures. They are not good for future-proofing our API. If anyone implements the method, then we'll break their code if we try to add additional parameters in the future. We should group the parameters into a single param (e.g. an interface with getters for each of those, saying in the interface's javadoc that users are strongly discouraged from implementing it and that additional properties may be added in future releases).

Maybe the right signature is `onApplicationEvent(String applicationId, ApplicationMetadata metadata, ApplicationEvent event)`. The reason being: applicationId is the uid of the app; the metadata tells us details of the app; the event describes the state-change that is happening for the app.

The same argument goes for `onLocationEvent`.