[Getdp] New wiki example, inductivity coaxial cable

[Kubicek Bernhard]

Hello!

I made a new wiki example, where the inductivity of a coaxial cable with
thick conductors is calculated both numerically and analytically using
the magnetostatic field energy in 2D.

http://geuz.org/getdp/wiki/InductivityF0

Of course this is only true for small frequencies. 

It would be quite nice if somebody someday could extend this example to
include (a non-analytical) skin-effect at high frequencies. 

very nice greetings,
 Bernhard