Remove annoying debug message.
Fix function_clause errors on console output.

While there was no side effects visible to the user, the application
should return {halt, Req, State} not {true, Req, State}.

Halt ensures that there is no more processing to be done on this request.

I also forced all the dispatch functions through the json handler.
Add the device handler, and getting all devices.
Fix tests to return decoded body, since body is always json.
Match /device/<id>/all specifically for all.