when sending of notification fails throw an error

Problem/Motivation

I occasionally have push notification tokens hanging around after they are no longer registered and would like to be able to clean them up. My logs could get filled with "Failure message: NotRegistered" messages

Steps to reproduce

Have a push notification token remain in the system after it is unregistered in the

Proposed resolution

have the send() method accept $throw_error = FALSE as a parameter so those who wish to use it can receive the error returned from Firebase.

Remaining tasks

create a patch

User interface changes

none

API changes

add an optional parameter to the interface and all child classes

Data model changes

none