In order to detect if a barcode scanner is being used, we detect the
delay between keypresses. The value is hardcoded to 55 ms. However, in
the case of a bluetooth scanner, this delay is often not enough,
resulting in an incorrect capture of the barcode.
We add the config parameter `barcode.max_time_between_keys_in_ms` which
allows the user to fine tune this delay for his hardware.
opw-806398
