Use title, if present, for playlist mainline

This is my first ever pull-request on GitHub, so I start simple :-)

For streams it is common for the filename to be something generated and
non-descriptive. If metadata for title exists, it is likely to be more
accurate. For streams specified in .pls playlists, this will use the
Title line.
This is also how the MPD web client in Volumio (Raspberry Pi) works.