Add option to reverse URL hint numbering

Summary:
Adds option to reverse the order of URL hints such that the last URL
(the bottom-most one) has the number 1 and the numbers increase from
bottom to top.

This becomes particularly useful when watching a log or buffer, or in terminal
chat applications. Very often, the most useful URL is the most recent one and
if there are many (> 10) URLs on the screen, the desired one will not get a
hint. Reversing the numbering makes the most recent URL hint take the number 1,
while the oldest will have the highest number or no number at all.

Reviewers: Konsole, VDG, hindenburg

Reviewed By: Konsole, hindenburg

Subscribers: hindenburg, ngraham, konsole-devel

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D15362