Calculation for a spectrum of wavelengths

```
Implement convenient simulation of spectrum, either inside of ADDA, or with
a separate script. Possibly optimize calculation by simultaneous solving
for many wavelength values in one iterative sequence  (should be especially
relevant in case of Rayleigh particles).

```

Original issue reported on code.google.com by `yurkin` on 24 Dec 2008 at 7:05
