Reimplement UmsCollection without cruft.

removed UmsHandler etc.

This new UMS plugin uses the Amarok collectionscanner. It is possible
to store the batchfile so scanning is not required unless something changed.

Other changes:
  * Add MemoryMeta convinience class.
  * Don't put UMS stuff in Collections namespace.
  * Add filename scheme to the UMS config dialog and user TrackOrganizer class.

TODO:
  * View errors in the collection browser. Needs looking at by experienced CV/QM person.

CCMAIL: amarok-dev@kde.org
GUI:UMS configuration changes
DIGEST:Completely reimplemented USB Mass Storage media device plugin