kpa-thumbnailtool --vacuum

Hi,

I've now implemented the "--vacuum" option to kpa-thumbnailtool. This option 
rewrites the thumbnail storage files, removing all unreferenced thumbnail data 
in the process (By design, the thumbnail cache can only grow and never frees 
any disk space during normal operation).

For me, this freed about 20% (250MB) of space - YMMV.

At his stage I'm pretty confident that this will not cause problems, but to be 
safe you can back up the '.thumbnails' directory inside your image directory.

If you can try this out and report your findings, please do so!

Cheers,
  Johannes