Save the application categories in GsApp

We'll need this if we want to show the menu in the details panel.
Save the application menu path in GsApp

We'll need this if we want to show the menu in the details panel.
Split up the menu spec plugin and refine the menu-path

The categories has to be done early, and the refine has to be done after the
AppStream plugin.
Show the menu category in the application details panel
trivial: Relax the licence length requirement a little
Correctly get the installed size of installed applications

Some backends do not append the origin to all IDs.