Continuous polarizability

[GoogleCodeExporter]

Implement continuous polarizability (not discrete values, as now), change
-read format accordingly. Possibly implement full tensor of polarizability.
This will open way to many new features, in particular Weighted Discretization.

Original issue reported on code.google.com by yurkin on 26 Nov 2008 at 8:16

• Blocking: Improve accuracy at backscattering direction #167, Self-term for particles near surface #180