Consider adding time filters to DataSetResults

[ericnost]

Most programs have records back to 2001 or even earlier. We already filter out records prior to 2001. We could consider adding an optional argument to store_results() for users to specify a time frame.

For instance:

ds = make_data_sets(["SDWA Serious Violators"]) # Create a DataSet for handling the data
recent_violators = ds["SDWA Serious Violators"].store_results(region_type="Watershed", region_value=["01412422"], timeframe = [2018, 2023]) # Store results for this DataSet as a DataSetResults object.
seneca_sdwa.dataframe

timeframe could take a list where the first value is the start and the second value is the stop (inclusive or exclusive).