Fix description, add new fields to command (cwd and disabled_for_archives).

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@820 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Do not scale_simple images if no actual scaling is needed.

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@821 ef8490bc-f317-4725-81ed-e95a9aca1bcf