Draft: install-script: new Mageia autoinst jeos script

Create a new jeos install script for Mageia using the automated installation method provided by DrakX [1].

[1] https://wiki.mageia.org/en/Auto_inst

Use it in mageia9, and add a small test for it.

How to test:

• in mageia9, add an installation tree like the following:

    <tree arch="x86_64">
      <url>http://distro.ibiblio.org/mageia/distrib/9/x86_64/</url>
      <kernel>isolinux/x86_64/vmlinuz</kernel>
      <initrd>isolinux/x86_64/all.rdz</initrd>
    </tree>

  it is needed because currently Mageia does not have a generic mirror redirector: users have to pick their own mirror manually, and we cannot set one in osinfo-db (otherwise it would "defeat" the point of a mirror)
• start an unattended installation with virt-install or GNOME boxes

TODO:

• test l10n/locale parameters more
• figure out more the compssListLevel & compssUsersChoice options
• test the installation more, and tweak the script as needed