Option to Use Subtitle, Series, SeriesID in Downloaded Title

[Budlyte]

Currently the book title is the only thing used for the filename in downloads, leaving no indication what number in a series each book is. Also, Title & Subtitle were parsed from the filename, then books from the same series all end up with the same name.

If the "series" & "seriesid" were checked for and added as variables in AudioDownloader.kt, then the final result could look like below.