Allow different global rulesets for different actions

[evinnichenko]

Usually, I set the extension to "image tabs only" and use it with "left/right/all tabs". However, sometimes I want to download all images from the current page (and doing it for all pages would be way too inconvenient), so it would be good to have an option of differentiating the two actions; eg "current tab" works for all images on current tab, and left/right work for image only tabs - or something else, as defined by user.