Added Peaking-EQ and Allpass filters

[yacinbm]

Added All-Pass and Peaking-EQ filters based on the Audio EQ Cookbook.

Please find attached the frequency response of both filters as generated by test_band_pass_filter_frequency_response.

All-Pass Frequency Response

Peaking-EQ Frequency Response

[yacinbm]

@yamadapc by the way, I was wondering how we could implement a band shelf. I was thinking we could substract an upper high shelf from a lower high shelf filter.

That way, we should be left with a frequency response that goes up from the lower cutoff, and down again at the upper cutoff. What do you think?

Edit:
Found an implementation derived from the RBJ equations here. Will study these to try and figure out how they were obtained. Will try to update this PR once I'm satisfied with the math :)

[yamadapc]

That seems good. I will merge this and publish in a bit.

I'm not sure regarding your band-shelf implementation idea but all of the filters crate is ported from this DSPFilters C++ project from vinniefalco.

[yacinbm]

That seems good. I will merge this and publish in a bit.

I'm not sure regarding your band-shelf implementation idea but all of the filters crate is ported from this DSPFilters C++ project from vinniefalco.

Sounds good, I will open a new PR for the band-shelf filter when I come around to doing it :)

[yacinbm]

After a little more research, I came to realize that peaking-EQ filters are the exact same as band-shelf filters! I'll leave it up to you to decide if we should rename the new peaking-EQ filters as band-shelf, as this is how vinniefalco named it. If you let me know, I can update the PR to reflect this :)

[yamadapc]

I see. Perhaps band-shelf would be more consistent with the other filter names, since they are all pass/shelf/stop names. I can rename too when I merge though.