Feature: Tag image action

[dixflatlinr]

Add a tag image option () which marks/selects an image. So when you browse a handful of images you can tag the ones you like.

• The tags are remembered upon exiting the program.
• Tagged images in the current folder can be selected by calling the Select Tagged Images (CTRL+) action.
• Would be nice to do various things with these images, like cutting them and pasting them to another folder, delete etc.