added new options to set the behavior if unprocessed images are found.

Right now a popup window will appear all the time if unprocessed images are found.
This is annoying after a while, even for me :-)

The new settings will control the way the plugin handles those images:
Ask the user - same behavior as before
Keep - do not remove unprocessed images
Remove - well, this would remove unprocessed images :-)

This is really helpful when playing with the advanced settings and you don't want to be bothered by the popup window all the time.