extract: Use TrackerStorage to check if file is in a removable medium

This will initialize a TrackerStorage on init and unrefs it on shutdown.
Removed warnings for missing TrackerStorage. Uncommented
media_art_copy_to_local which now works again.
tests: Fix includes
build: Fix distcheck
Rename LICENSE to COPYING, and add COPYING.LESSER

Autoconf adds COPYING which contains GPLv3, which is not what the
sources are licensed with.  Replace it with GPLv2 in a text file
from GNU's website and add COPYING.LESSER for LGPLv2.1, so that the
package would be under LGPLv2.1 license.