Add Wind/3DP support

[jgieseler]

• Requires latest version of wind-3dp-loader (as of today)! Install with pip install git+https://github.com/jgieseler/wind-3dp-loader
• Wind/3DP has eight viewing directions that are adressed with their corresponding number as a string, so viewing='0' to viewing='7'.
• For Wind/3DP, no channel combinations are supported as of now (because not needed for us). Thus, channels should only provide one integer (between 0 and 6).
• Wind/3DP energies and corresponding fluxes are originally given in eV instead of keV or MeV. In SPOT, a conversion is done for the finally used flux to MeV and for the energy strings to keV!
• Wind/3DP has a new parameter threshold (provided in eV!) to remove outlier fluxes that occur from time to time, e.g.:
• See also https://github.com/jgieseler/SPOT/blob/master/onset-notebook-wind-3dp.ipynb for an example onset analysis
• PS: Some linting in other code parts has been done

[jgieseler]

Additional information on viewing

Above, it's stated that Wind/3DP provides eight viewing directions ('0' to '7'). Important to mention is in addition that the specific directional information is provided in the returned pandas dataframe as pitch angle values in the columns 'PANGLE_0' to 'PANGLE_7'.

For example:

from onset_functions import *
path = '/home/gieseler/uni/wind/data/'
event_onset = Event(spacecraft='wind', sensor='3dp', data_level='l2', species='e', 
                    start_date=datetime.date(2021,10,28), end_date=datetime.date(2021,10,30),
                    data_path=path, threshold=None)
event_onset.df_e.filter(like='PANGLE').plot()