DAC paper algorithm updates

[nrs23]

#46 changes some of the acoustic index algorithm implementations after review from the team. The new algorithms now match seewave implementations and produce similar results, according to the new test suite.

If we're going back to the old dac paper branch for the paper (instead of bringing the last couple of dac paper algorithms into the new framework), then these algorithms need to be updated to the latest versions:

• spectral_flux: normalisation change and calculated over the power spectrum
• spectral_entropy: calculated using Welch power spectral density estimate, rather than an FFT with averaging over windows
• log(1-{f})", features=["temporal entropy"] calculation now includes a lower bound epsilon for the log calculation to avoid infs