SEP Sesam rear integration: code cleanup

Hi,

some more changes to the Sesam module integration:

 usr/share/rear/build/default/99_update_os_conf.sh
 
Make sure os.conf is created in the right place if REAR is not installed in default path

 usr/share/rear/lib/sesam-functions.sh

Move over the config parsing part to a common place and source it from the scripts needing it.

 usr/share/rear/prep/SESAM/default/40_prep_sesam.sh

Use the common script above, do not include sesam init scripts and various executables anymore

  usr/share/rear/skel/SESAM/etc/scripts/system-setup.d/59-start-sesam-client.sh

start sesam client directly, do not use the init script.

Thanks! :-)