Can compute the CSR impedance for free space and parallel plates model.
WakeFunction not implemented yet.

Allow to read both wake function and impedance with read_IW2D_folder
Fix yokoya_elliptic function

# Conflicts:
#	tracking/element.py

Change back invariant name to cs_invariant
Simplify SkewQuadrupole track method

Add comments.
Remove usage of bins, use only center.

Not needed any more due the SynchrotronRadiation change.

Fix bug on Beam.distance_between_bunches for the last bunch when the first bunches are empty.
Change Beam.distance_between_bunches to compute the array only at initalization with Beam.update_distance_between_bunches
Beam.mpi_share_distributions can now share all bunch dimensions.

Correct time decay !
Now ok versus for loop (decay then beam loading)

Typo in the type of data to share for bunch profile. Not sure if there was an effect.

In track method of cavity resonator, there was an additional phasor decay of bin length.
To avoid that the good boundaries are set bins[0] instead of center[0].
For now the bins are also shared in Beam.mpi_share_distributions

Add single core tracking for CavityResonator
Correct missing ref_frame is CavityResonator.track
Change phase of generator voltage to be the bin phase
Correct generator phase for non integer m
Change init_phasor track time to 10 times
Change phasor_evolution k to change order of steps

Add phasor initialization (on the "rf" reference)
Change beam phasor evolution to allow for "beam" or "rf" reference

Correct case when where is no mp in the bin
Remove useless test

Add tracking to CavityResonator based on the mbtrack implementation but using a analytic formula for speed-up
Add method to Beam to share longitudinal distributions
Add methods to Mpi to look for next and previous bunches
Add start of a CavityMonitor, to improve to deal with multi-cores

Remove for-loops inside the function.

- cs_invariant method in Bunch is renamed to 'action'.
- Action is now saved together with BunchMonitor and can be plotted in plot_bunchdata

Main change
- Variable local_beta, local_alpha, and local_gamma are made property objects.

Minor change
- Add an option to plot phase space in different style.

Remove part which was causing "damping".
We have to re-process the wake function at each track call and not to reuse the previously processed wake function

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

Bugfix due to switch to numpy arrays.
Allow to save less mp than the full number in the bunch.

Bugfix2 : PhaseSpaceMonitor

Fix dipole_moment due to switch to numpy arrays for Bunch.binning

Update docstrings
Use pd.DataFrame representation for bunch __repr__
Add the track_alive option for Bunch and Beam.init_beam