Improve the simulator for the greedy algorithm
Small changes to make it compatible with python 3

Small changes to make it compatible with python 3 at the same time it is
compatible with python 2.
Improve the print_statistics_table function
Raise SkipThisOne exception on IA algorithm error

If the MMSE IA algorithm raises a RuntimeError or a LinAlgError
exception and thus don't find a solution, then the SimulationRunner will
raise a SkipThisOne exception to skip the current repetition. Hopefully
in the next one (with new channel and precoder initialization) the IA
algorithm will find a solution.

This change makes the simulator robust ill conditioned conditions,
which will simply be skipped.
Fix wrong base_name in main_plot function
Merge branch 'greedy_simulator'

New improvements to the greedy IA simulator.