wraps _parse_timeseries_generic and call it for each period

[ruupert]

Understood from #346 that the API now returns each day as a different period with each period having the same index numbers.

So I figured that the easiest way is to just wrap the old function slightly modified and call it as many times there are periods, and collect the series, combine them into a single series and then return it.

running "python -m test" did return 0.

[ruupert]

this pr does have the resolution to pandas timeseries mapping problem which is fixed in #347 at

parsers.py:
freq_key = _timeseries_frequencies_to_timedelta(soup_series.index.freqstr)
series_parsers.py:
def _timeseries_frequencies_to_timedelta(freq_text: str) -> str:

[ruupert]

this with the time_mapping in parse_prices() from issue this solution works but logically _parse_timeseries_generic() should just parse like it says in the name, not return a resulting series.