Download by series, download by author

[taxilian]

Implements #183

My python is more than a bit rusty; I tried to follow existing patterns, but let me know if there is anything you need me to fix.

[mkb79]

It looks quite good so far. One point should be considered again. What if someone is looking for a title and author. Then only audio books should be displayed where the title and author match. Currently, he would search by title or author and add the results!

[taxilian]

That is true; I assumed that was the way you wanted to do it since that's how it's set up with ASNs and titles, but if you want I can probably figure out how to do an intersection instead

[mkb79]

Maybe the if match condition for authors, title and series should be merged. So first add only asins where authors, title and series match and then make the questionary?!