Bessel-Functions

[LoganAMorrison]

Need to implement Bessel-functions of first and second kind as well as modified and spherical Bessel functions.

[LoganAMorrison]

Cylindrical Bessel functions are finished.

use cyphus_specfun::bessel::{CylBesselJ, CylBesselY, CylBesselI, CylBesselK};
let x = 1.0;
x.cyl_bessel_j0(); 
x.cyl_bessel_j0_e();
x.cyl_bessel_j1();
x.cyl_bessel_j1_e();
x.cyl_bessel_jn(2);
x.cyl_bessel_jn_e(2);
x.cyl_bessel_jv(0.5);
x.cyl_bessel_jv_e(0.5);

and so on. The modified Bessel functions also support exponentially scaled versions:

x.cyl_bessel_kv_scaled_e();