integrate SEP Sesam backup software client into REAR boot image

Dear REAR maintainers,

we have re-arranged the sesam integration into rear in a more sane way
now, attached you can find the diffs against the current github
repository, here are the explanations for the changes:

>  Makefile                         |    6 +++---

a short patch to honor the DESTDIR variable during install-bin, so
REAR can work from a random directory it has been installed to
(make install DESTDIR=/tmp/installation/)

>  usr/share/rear/conf/default.conf |    9 +++++++++

add the default COPY_AS_IS_SESAM values to default.conf

> usr/share/rear/prep/SESAM/default/40_prep_sesam.sh |   63 ++++++++++++++++++++

this will detect a possible SEP Sesam client installation on the system and will include the sesam components needed to run a sesam client within the boot image. As SEP Sesam users have the possibility to either
install via RPM packages or custom .tar.gz packages it makes no sense to
use standard values like tsm or bacula, because the installation paths
are up to the user (with .tar.gz based SEP Client installation packages)

Auto detecting is done via /etc/sesam2000.ini which contains the paths
in both cases.

> .../restore/SESAM/default/40_restore_backup.sh     |   15 +++++

just a short note to the user how to proceed with the restore after
disk layout has been done.

> .../SESAM/default/90_create_missing_directories.sh |    9 +++

just a copy from the default workflow which helps here aswell.

>  .../system-setup.d/59-start-sesam-client.sh

a short script to start the sesam client via init script during boot
of the iso if it contains the sesam client.