Add support for logarithmic singularity (fixed-point) quadratures

[wa03]

See http://www.pmf.ni.ac.rs/pmf/publikacije/filomat/2016/30-4/30-4-28.pdf for details

I have an implementation using mpmath, but it feels like I'm being very inefficient about it.

[nschloe]

An interesting suggestion. I'll probably look at it at some point.

[wa03]

Let me know if you need any reference code or anything. Like I said, mine feels very inefficient, but I'm not familiar with generating quadratures, so maybe there's an obvious easy way to improve the approach I have.