Support Firebase Cloud Messaging (FCM)

[fahad86]

[chrishaff]

I would prefer this module support FCM as well.

I did however find comments elsewhere that https://github.com/caffeinalab/ti.goosh (Android) supposed to work with FCM. While the ti.network method works with iOS.

[Wingee]

It seems to work with FCM for Google, but using the iOS device registration id, FCM won't send a message to the device and says the registration ID is invalid. I assume FCM gives a different type of ID for iOS devices... it would be great if the module could be updated to get a valid FCM ID for iOS