Normalize waveforms
I have added the argument normalize_wav to the following classes and functions (which all handle loading of audio from wav files),
- Waveform.from_wav
- MagSpectrogram.from_wav, PowerSpectrogram.from_wav, MelSpectrogram.from_wav, CQTSpectrogram.from_wav
- AudioLoader, AudioFrameLoader, AudioSelectionLoader
- create_database
If normalize_wav=True, the waveform will be normalized so it has zero (0) mean and unity (1) standard deviation. The default value is normalize_wav=False (ensures backward compatibility).
I have also expanded the audio representation parser to handle this new argument.
Unit tests have been created and are all passing.
Should be ready to merge. Please have a look, thanks