[x] discard all data before e.g. introduction of afsluitdijk as part of kw.read_measurements() with values in physical_break_dict.
[x] slotgemiddelden it is useful to also plot the yearly mean values, but only take the fit over the years after the physical break, so make part of the slotgemiddelden and overschrijdingsfreq functions, not of read_measurements >> do this as part of clip_timeseries_physical_break
kw.read_measurements()
with values inphysical_break_dict
.