Mo subprocess

The micromegas python does not use a shared library object for an interface to Micromegas anymore.

It turned out that Micromegas (version 2.4.5, but this is not likely to change) accumulates open shared objects.

This was verified as follows:
 * cd <MICROMEGAS_DIR>/MSSM
 * comment out "#define SUGRA"
 * make main=main.c
 * valgrind --leak-check=full --track-origins=yes --log-file=log.out --show-reachable=yes ./main slha-file.txt
* In log.out you'll see that a lot of memory is still reachable. 

This is not a leak per se, because this memory doen't go out of scope, but in the context mastercode this was found to accumulate.

This behaviour is circumvented using subprocess. The output then gets read and the relevant observables are collected.