Add simple SINR simulator for a METIS scenario

The scenario is an indoor case with rooms in a building and one access
point in each room.
Simulate the METIS scenario for discrete positions
Add visualization for the SINR in each room
Add an IPython notebook for METIS scenario
Improve color  plots in simulate_metis_scenario.py
Improve IPython notebook for METIS scenario

Reorganize the code and add an interactive plot.
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 'master' into METIS_Scenario
Change calc_wall_losses to calc_num_walls

In order to calculate the wall losses just multiply the output of
calc_num_walls by the loss (in dB) for each wall.
Add PathLoss(Indoor|Outdoor)Base classes

Add PathLossIndoorBase and PathLossOutdoorBase classes.
Remove **kargs from outdoor pathloss classes
Add the 'type' property to path loss classes

This is useful mainly for introspection.
Add missing classes to __all__
Improve docstrings in pathloss module
Merge 'PathLossRefactorings' into METIS_Scenario
Add get_latex_repr to the PathLossMetisPS7 class
Change a division to a float division

Change a division in the PathLossMetisPS7 class from "/5" to "/5.".
Add simulation case with the METIS path loss model
Change a division to an integer division

The result of the division should be an integer, since it will be sued
as an index.