sketch from Artyom
remove equipment from registration data to make it less than 254 bytes!

make separate function to send button notifications!
introduce Arduino-friendly names to the InputMessage and OutputMessage
aux method to put non NULL-terminated strings. also prevent strlen() to call twice if string length is already known.
use stream writing for writeRegistrationResponse() method

since registration data could be very big (more than MAX_MSG_SIZE or 256 bytes) we cannot use OutputMessage to send registration data.
in this case we use "stream write" operation to do the same thing!
get equipment back to registration data