Add options "Selected games" and "Filtered Games" to bulk download

[HerrKnarz]

Describe the solution you'd like At the moment, it's impossible to download HLTB data in bulk for only a specific selection of games. It would be great, if the "Download plugin data..." dialog also had the option for "Only selected games" and "Only filtered games". That would make downloading data in huge libraries a lot easier and should be very simple to implement.