histedit: define new colour pairs for roll action Red seems like a good colour to indicate removal, since that's the colour we use in diffs. We need three varieties with three different backgrounds corresponding to the possible ways we can display a rule.

histeditrule: split __bytes__ property into prefix and desc In order to be able to colourise the description of the rule, we need to have it as a separate bytestring. Curses doesn't make it easy to take existing text on the screen and give it different properties; we can only add new text with new properties.