uniax.py shows uniaxiax tension/compression test on concrete specimen with
optional confinement.

Run using yade-multi and confined.table (see comments in that file) to run
simulation with different confinement values.

Run plain uniax.py to get one unconfined tension/compression simulation.
Type yade.plot.plot() to see strain/stress plot during the simulation.

See comments at the beginning of uniax.py for more information.

The periodic.py is uniax.py, but running on a periodic sample.
