Improve plot_deterministic_path_loss_in_dB

The plot_deterministic_path_loss_in_dB method will now respect the
handle_small_distances_bool attribute.
Add latex representation to path loss classes

This is useful for displaying in path loss objects in an IPython
notebook.
Add an IPython notebook display path loss classes
Add PathLossMetisPS7 class
Fix bug in calc_wall_losses (wrong diagonal loss)

Fix a bug in calc_wall_losses where diagonals were not counted as two
wall losses.
Small improvements to the METIS IPython Notebook

Small improvements to the METIS scenario IPython Notebook.
Merge branch 'METIS_Path_Loss'

Merge branch implementing the Propagation Scenario (PS) 7 path loss
model from the METIS project.
Merge branch 'master' into METIS_Scenario