Firefox playlist sorting fix (issue #42)

Added the 'helper: clone' option to jQuery sortable, to prevent an item from being played when attempting to sort a playlist. This issue seemed to happen only with Firefox, at least on Ubuntu. It works fine now on my Ubuntu machine.

I'm new to using Git so I included the 'database.yml' config file by accident. However the change involves one line in 'playlist.js' so feel free to ignore this pull request if it's a problem.