Clean up live installer remains and add net installer icon:
- Remove correct_live_install, correct_live_for_reboot and
xdm-liveinstall.patch
- Add installation.desktop and start-install.sh
- Use tumbleweed template instead of 13.2

In KDE, the installer has an icon on the desktop. Installation tested, boots fine.
In GNOME, it appears as "Installation" in the dashboard search. YaST appears, installation itself not tested.