WakePotential -> add method to plot wake potential for a perfect gaussian bunch
utilities -> new function gaussian_bunch which gives the gaussian bunch profile
utilities -> read_IW2D now also reads wake function from IW2D
utilities -> new function read_IW2D_folder which reads the full results folder of IW2D into a WakeField element.
resistive_wall -> change the sign of the wake functions to agree with the code convention

The exact wake function for the transverse wake function is wrong (from paper) ! Need to find a better expression.

Remove tools.py to avoid circular import problem with wakefield.py -> merged into wakefield.py
Remove machines folder to save machine data in a seperate git instance
Rework import so the code can be used as independant module mbtrack2

Add a ImpedanceModel object which derives from Element and is used to sum up different Wakefield elements
Fix uppercase module in resistive_wall.py

To be PEP8 complient:
Lowercase folders
Extended docstrings
Rename and divide some files