Save and load methods allow to save Bunch and Beam object and reload them later on.
Load method for Beam allow to choose if mpi is used or not.
Initial modification from Watanyu.

Change sign of the imaginary part of the impedance in the Coating class to agree with mbtrack2 convention.

Plotting function for longitudinal coupled bunch stability diagram for any set of CavityResonator objects.
Add loaded shunt impedance property to CavityResonator.
Change CavityResonator.Z method to use loaded shunt impedance.

Switch from interp1d to np.interp

WakeField.drop allows to delete a component or a list of component from the WakeField.
WakeField.save and WakeField.load add a shortcut to pickle WakeField objects.

Both Impedance and WakeFunction now inherit attributes from ComplexData (component_type, power_x, power_y, ...)
Add a components property to WakeField which lists all components present (W and Z)
Adapt other classes using Impedance and WakeFunction to the change.

# Conflicts:
#	mbtrack2/tracking/__init__.py

Damper class are now active on a single plane at a time

Improve WakeFunction and Impedance methods to better take into account transverse wakes.
Update read_IW2D function to account for pandas library changes in the last versions.

[Fix] Bug when FIRDamper was used to track a Beam without MPI.
Various docstring modifications and code reformating.

remove FeedBack.py file

Add feedback.py file

Add a new example notebook on RF cavities and longitudinal beam dynamics which explain the RFCavity, CavityResonator and BeamLoadingEquilibrium classes.

Add cs_invariant to plot_beamdata, plot_bunchdata and streak_beamdata

Add n_bin optional parameter for CavityResonator used only if mpi is false.
Various docstring improvements.

Add Courant Snyder invariant monitoring in BeamMonitor
Add a bunch_cs method to Beam

Set hdf5 file to "a" mode fix an issue where the ProfileMonitor in MPI mode hung when writing data.
Remove flushing in ProfileMonitor.write() to avoid hung issuse in MPI mode.

Fix Monitor.track_bunch_data method to check that only the bunch which bunch_num is specified can write on the file
Modify the behaviour of BunchMonitor, PhaseSpaceMonitor, ProfileMonitor
Make the same modification within WakePotentialMonitor.
Style change to BunchSpectrumMonitor

Remove ipynb file from gitignore

move down init

Add requirements.txt for pip install
Update mbtrack2.yml to add accelerator-toolbox dependency for lattice import

Fix plot_phasespacedata and plot_profiledata
Change color map for streak plots for plot_profiledata, plot_wakedata, plot_cavitydata

Add utilities and instability folders
Change folder name from collective_effects to impedance