Synchronize GNOME based Linux gsettings into common script

Synchronizing 01-systemsetup.sh scripts by moving gsettings to a new configure-gnome-shell.sh common script.

Also refectoring 01-systemsetup.sh content to have similar content (i.e. configure-gnome-shell.sh is called before grub changes) which could help later refactoring towards common script.

Other findings:

• Also org.gnome.mutter settings could be moved into same common
  script, but noticed that openSUSE didn't have mutter package by
  default like Ubuntu, RHEL and SLES has
• Therefore that change is not yet moved to GNOME based linux common scripts
• If needed - It could be done later, with suitable solution

At some point this kind of refactoring towards common scipts could be done more in wider perspective - with scripts which content is currently quite generic, like this 01-systemsetup.sh has.