Update the 'How to use larda' in documentation

[martin-rdz]

Some examples are not longer working as expected (mostly due to minor changes in larda or dependencies).

E.g. the xarray resample and plot example is

larda_rsd2.connect('lacros_cycare')
begin_dt = datetime.datetime(2018, 1, 15, 0, 0)
end_dt = datetime.datetime(2018, 1, 16, 0, 0)

iwv = larda_rsd2.read('HATPRO', 'IWV', [begin_dt, end_dt])

iwv_xr = pyLARDA.Transformations.container2DataArray(iwv)

iwv_resampled = iwv_xr.resample(time="1H", keep_attrs=True).mean(keep_attrs=True)

fig, ax = pyLARDA.Transformations.plot_timeseries2(
    iwv, figsize=[7,4], label='instrument resolution')
fig, ax = pyLARDA.Transformations.plot_timeseries2(
    iwv_resampled, tdel_jumps=4000, step='post',
    linewidth=2, label='resampled to 1h',
    fig=fig, ax=ax)
ax.legend()

while the working version in the newest version would be

larda.connect('lacros_cycare')
time = [datetime.datetime(2018, 1, 15, 0, 0),
        datetime.datetime(2018, 1, 16, 0, 0)]

iwv = larda.read('HATPRO', 'IWV', time)

iwv_xr = pyLARDA.Transformations.container2DataArray(iwv)

iwv_resampled = iwv_xr.resample(time="1h").mean()

fig, ax = pyLARDA.Transformations.plot_timeseries2(
    iwv, figsize=[7,4], label='instrument resolution')
fig, ax = pyLARDA.Transformations.plot_timeseries2(
    iwv_resampled, tdel_jumps=4000, step='post',
    linewidth=2, label='resampled to 1h',
    figure=fig, axis=ax)
ax.legend()