Specifying --low-key with negative octave values doesn't work

[HelgeKautz]

samplescanner: error: argument --low-key: invalid note_number value: 'C-2'

My U-220 can receive C-1 as the lowest note, while Apple Mainstage seems to represent that as C-2. I suppose this is just a mapping difference between hardware, Mainstage and SampleScanner. An Option to adjust that would help, so that incoming note numbers are transposed accordingly.