Add support for RCS

[ericnewcomer]

If messages are sent via RCS, the Android Channel will miss the notification since it will be sent as an RCS specific broadcast.

For now, at least one user says that at least on the Galaxy S8 stock app, there is an option to not use RCS. So until this is implemented, that is the current guidance.

From user:
So, I went to the stock messaging app, then settings, then to Chat settings, change the default message type to Text/Multimedia Message (and not Chat message, which is RCS I suppose).