Replace `band_base` code
Need to send out proposition for vote.
Original propositions (with criticisms) were:
Original
band_base: <string> # must be "B" or "S"
Users didn't understand why other band_codes couldn't be used. I did so that they wouldn't always expect the band code to be what they put in
First proposal
Provide broad_band: <boolean>
Others pointed out that some instruments have no "broad_band" option and that their "band_code" is actually fixed (e.g. "LOG" channels)
Second proposal
Provide either broad_band: <boolean>
or band_code: string
Allows for fixed band codes but complicates validation (either/ors are ugly to handle in JSONSchema) and might be even more unclear