Implement get_ap_positions

For now the METIS simulator only works for a decimation value equal to
1.
Change METIS simulator to use ap_decimation

The METIS simulator now has other access point distributions besides
only the previous 1 AP per room.
Remove the axis of the imshow plots
Move most of code in "if __name__" to a function

This allows better reuse of the simulation code in the
simulate_metis_scenario.py in the corresponding IPython notebook.
Ignore the .idea folder created by PyCharm
Merge branch 'Flexible_APs'