Hints for qupzilla in main

Warnings

• ancient-metadata
  The AppStream metadata should be updated to follow a more recent version of the specification.
  Please consult the XML quickstart guide for more information.
• screenshot-save-error
  Unable to store screenshot for 'http://www.qupzilla.com/screens/gnome.png': Can not store source screenshot: Failed to load image data: Unrecognized image file format
• screenshot-save-error
  Unable to store screenshot for 'http://www.qupzilla.com/screens/dial_gnome.png': Can not store source screenshot: Failed to load image data: Unrecognized image file format
• screenshot-save-error
  Unable to store screenshot for 'http://www.qupzilla.com/screens/preferences_gnome.png': Can not store source screenshot: Failed to load image data: Unrecognized image file format