Added handling for upgrading GNOME selected as default desktop

- bnc#874116
Changes and version
Merge pull request #29 from kobliha/desktop_software

Added handling for upgrading default desktop using software->upgrade->window_managers
Explicitly selecting 'minimal' pattern for installation

    - bnc#875350
    - selection can be removed manually by user if needed
Merge pull request #30 from fcrozat/master

Explicitly selecting 'minimal' pattern for installation
remove addon client as it is now run from scc client
release
Merge pull request #31 from yast/remove_addon

Remove addon
Revert "remove addon client as it is now run from scc client"

This reverts commit 2abc494c9fe96529e08f67ddfb38ef5f565a4723.
display the addon dialog by default
changes

- 12.0.29
Merge pull request #32 from yast/add_on_step

Add on step
remove non-existing clients from auto-upgrade workflow
Merge pull request #33 from yast/fix_autoupgrade

remove non-existing clients from auto-upgrade workflow
return back proposal entry for autoyast clonning (bnc#881108)
Merge pull request #34 from yast/clone_proposal

return back proposal entry for autoyast clonning (bnc#881108)