Allow service extension

[btkelly]

I removed the service declaration from the library manifest file as it did not allow extension of the WearableListenerService (you can only have one). Now users must add the service declaration manually but it allows extension and specific event listening inside the WearableListenerService.

[tajchert]

But this is much less convenient as you need to add this each time to Manifest + more chaos in Manifest. Pefect would be not overriding tag for gradle (so if there is WearableListenerService service declared it doesn't override it, but require you to call manually some methods in BusWear itself from WearableListenerService).

It was like this in very first version of BusWear.

[btkelly]

I added information to the README to account for that but I get not wanting to complicate the setup of the lib.

So my use case was I only have a WearListenerService on the handheld and Activity listeners on the wearable. I needed a WearListenerService on the handheld to process my own logic so I had two services which, as you know, is not allowed.

Maybe an alternative would be adding the ability to hook into broadcasts of some sort that the built in WearListenerService would fire? What do you think? Currently I am running my fork of the lib as I need to be able to hook into those events.