Do not print a warning when new versions of appdata-tools are installed
Set the project group in the GsApp

Filtering the packages in the plugin is the wrong layer.
Only filter incompatible project groups when searching

We still want to show the extended descriptions on other desktops, for instance
showing the full description for gedit if using XFCE. If we filter the list only
when searching then gnome-software does the right thing in more cases.