Consider playlist song count limit

[crohrer]

There might be a limit at 10,000 Songs per Playlist. It surely takes a long time to reach that, but maybe the script could handle this?

[crohrer]

Instead of adding a number in a postfix to archived playlists, better add a date.
So instead of " (archived 1)" use " (archived 2016-01-21)"
This implies that the new playlist doesn't necessarily check for duplicates in old lists (like it was originally planned & which turned out was not that practicable)
This also fixes the problem that a deleted archived playlist could cause the postfix number to get duplicated.