MACHINE NAME and FIRMWARE_URL in configuration.h

This allows MACHINE_NAME and FIRMWARE_URL to be optionally set from
Configuration.h rather than modifying language.h. This is mostly useful
for manufacturers to set MACHINE_NAME and point FIRMWARE_URL to their
own fork, without making the list unwieldy and hard to parse in
language.h due to every manufacturer adding themselves in the upstream
repo or creating merge conflicts because they don’t.