Added option argument for Item.find_by_filter_values

Hi Andreas, cfr to the podio help topic -> https://help.podio.com/hc/communities/public/questions/200519048-Podio-API-Why-don-t-item-files-appear-when-using-filter-?locale=en-us I'm filing a pull request to add an options argument to the find_by_filter_values. I tested everything. If there is anything I need to change, please say so.

Greetings,
PJ