Man page edits for output locations
Add --trim-history option

All download history entries older than --trim-history value will be
deleted.  Cannot use 0 - use 'all' to completely delete download
history.  --trim-history short-circuits all other commands.
Added --tag-id3sync

--tag-id3sync saves ID3 tags for MP3 files in synchronised form.
Provides workaround for corruption of thumbnail images in Windows.
Has no effect unless using MP3::Tag Perl module.
Updated user agent strings

h/t sthen
Handle series with "series" in name

h/t rdixon