Add transmission-qt to the transmission package?

[Bodertz <bodertz@gmail.com>]

The transmission package (the transmission:gui output specifically) has
transmission-gtk, but I personally prefer transmission-qt.  By including
qtbase, qttools, and qtsvg, transmission-qt will also be built.

I've made a simple package that inherits from transmission to do this:

    (define-public tranmission-qt
      (package
       (inherit transmission)
       (name "transmission-qt")
       (inputs (modify-inputs (package-inputs transmission)
    			  (append qtbase qttools qtsvg)))))

This works, except that transmission-qt.desktop is moved to the gui
output due to the inherited 'move-gui phase.  I could figure out how to
remove that phase to fix that, of course.

But I'd prefer if transmission-qt were an option for the transmission
package directly, either under a new :qt output, or to have both
transmission-gtk and transmission-qt under the :gui output.  Or just a
separate package, transmission-qt.

Any thoughts on that?