Remove stray com.redhat.Cockpit.conf file

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
Remove unused .gitmodules file

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
Remove old adwaita scss file

Closes #489
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>