Refractive index of the medium

[GoogleCodeExporter]

Implement specifying refractive index of the medium by command line option.
It will simplify application of ADDA to such cases reusing existing files
with refractive index spectra, etc.

Since absorbing refractive index of the medium is fundamentally hard, first
step is to limit the command line argument to real values.

Original issue reported on code.google.com by yurkin on 9 Dec 2009 at 8:49

• Blocked on: Radiation forces in surrounding medium #29

[myurkin]

It is also interesting to look into the possibility of tensorial (anisotropic) epsilon of the medium. But that requires proper formulation of the scattering problem in the first place.