diff configure @ 589:7ebd5a21d74f sonification

Branch to handle audio feedback and metadata sonification interactively with the UI.

Piano keyboard audio feedback:
The midi pitch of a piano keyboard note is retrieved in SpectrogramLayer::processMouseEvent when a left click is made on the note in the Select tool mode (SpectrogramLayer with a log frequency scale). The same process should be applied to the Spectrum layer (log frequency scale) as well.