Allow changing axis labels on the 2D Spectrogram

[RosaryMala]

Currently, the spectrogram has a pitch label on the left, and a db label on the right.

It'd be useful if the left and right axes could be changed, to be either swapped, or changed to a different scale entirely.

[tlecomte]

Thanks for the report @RosaryMala. May I ask why this would be useful ? Is it maybe because other programs do it this way ?

[RosaryMala]

In the five years since I've made this report, I no longer remember...

[tlecomte]

Sorry about that, it's my fault for not reacting in a timely manner.

I'll close this issue as stale then.

Thanks!