0.16.0

Main changes:

• Images can be resized now.
• Added image size and path to statusbar.
• Error messages are shown if saving with a format is not supported.
• Prevent users from defining ambiguous shortcuts.
• Added an action for copying paths.
• Start the app on the screen with mouse cursor when opening images.
• Support all image types that Qt supports (previously, only "image/…" was supported).
• A depreciation notice is added to screenshot command line options.