the word 'Flagger' now is History, we have 'Flags' now (except for plotting, which is old and deaf and probably die soon anyway)

also removed peculiar neg-operator

 - inverse interpolation
 - inverse aggregation
 - shift
 - resample

fixed constants detection. -there was the famous `ramp-up` error, because of the laggy implementation of pd.rolling ;)

refactored drop_flags to to_drop as former implies a boolen value, but a array-like or scalar is expected.