imagecache 6.x-2.0-beta4

Changes since DRUPAL-6--2-0-BETA3:

• #353148 by schildi: imagecache update_4: "ALTER TABLE" executed twice.
• #304376 by Roger López, beholder and drewish: Update function from 5.x -> 6.x.
• Fixing some warnings in the imagecache_ui.module.
• #335780 by drewish: Actions define $image as passed by reference, but call_user_func doesn't support this.
• #298555 by mleicester and drewish: Prevent any image manipulation where a preset has no actions.
• #318430 by dman and drewish: Show a 'preview' image when editing imagecache presets, for easy testing.
• #322155 by thePanz: Pass class attribute to the non-linking formatters.
• #331400 by Steve Dondley: Document the need to grant permissions to presets in README.txt.
• #297230 by joachim: Typos in preset description text.