Don't create launch shortcut entry for non-applications

We want to be able to define shortcuts for system services by dropping deskto files in /usr/share/kglobalaccel

This is already mostly possible, except they would get a 'Launch' entry in addition to the action entries.

That is undesireable for many use cases because the relevant component is a system service, not a user-facing and launchable application

Introduce a new X-KDE-GlobalShortcutType=(Application|Service) key and only add the _launch shortcut for Application

For compatibility with existing files assume Application when the key is not present