include additional beam (decoder) measures

[joslloand]

Zotter conveniently offers a variety of additional (analytic) beam measures here:

Ultraspherical/Gegenbauer polynomials to unify 2D/3D Ambisonic directivity designs

• pressure (P)
• energy (E)
• quality (Q, directivity)*
• rV
• rE
• fbr (frontBackRatio)

*Is another name used for this in the literature?

Methods would most likely be added to HoaOrder.

sc-lang implemenations can be found here.

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NOTE:

• rV, rE for currently implemented beams are according to Daniel.
• rV, rE for additional beams would require these algos.