trivial: Add some profiling to try to find the desktop file slowdown
Do not load SVG icons when parsing desktop files to speed up startup

Using the icon cache shaves 900ms off the coldstart time when getting the
installed list.
trivial: Use --show-results when using gnome-software-cmd
trivial: Allow profiling the updates using gnome-software-cmd

Wowsers. 12 SECONDS to query the updates list using yum.