Support multiple filters in CDX search

[Mr0grog]

The filter_field parameter for WaybackClient.search() can now be a list or tuple of strings, letting you add multiple filters. For example, to search for all captures at nasa.gov with a 404 status and “feature” somewhere in the URL:

client.search('nasa.gov/',
              match_type='prefix',
              from_date=date(2022, 1, 1),
              to_date=date(2022, 2, 1),
              filter_field=['statuscode:404',
                            'urlkey:.*feature.*'])

Thanks to @BilibalaX for starting this in #120.