Hilbert PDN - consider implementing Hutchins design method

https://github.com/mtmccrea/Hilbert/issues/17

> Bernie Hutchins provides a discussion of PDN design here:
> 
> [Electronotes 168 90 Degree Phase Differencing Networks - 7 pg](http://electronotes.netfirms.com/EN168-90degreePDN.PDF)
> 
> Offers a method to calculate poles for arbitrary _Order_ and _Bandwidth_.
> 
