Merge from vendor branch TNF:

Merge from vendor branch TNF:
import nelma-3.0

Nelma is a (command line) tool for numerically calculating various
electrical properties of printed circuit boards or similar objects
composed of conductors and dielectrics (however code is optimized for
circuit board-like geometry).

It is currently capable of calculating capacitances between objects -
nets on a PCB. It returns a spice-compatible description of an
equivalent circuit of stray capacitances that can be for example used
for more accurate circuit simulation. Alternatively it can also
produce field data that can be plotted for example with Gnuplot.

Support for calculating resistances existed for a while but was later
removed because it didn't receive much testing.

Nelma is available under the GNU General Public License version 2.