Add xdg-browser or xdg-www

Submitted by Vincent Untz @vuntz

Assigned to Portland Bugs

Link to original bug (#33055)

Description

It was pointed out that it's sometimes needed to just start the browser, without an URL. So xdg-open cannot be used for that.

Mandriva had a script for this: http://svn.mandriva.com/cgi-bin/viewvc.cgi/soft/desktop-common-data/trunk/bin/www-browser?revision=243941&view=markup