Corrected log file handling and added variable for service name.
Included installation of default configuration for back ends. Included copyright notice. Added small installation progress output. For clustered or distributed installations, the installer now emits strings for usage during installation on remote hosts for additional back ends and additional front ends.
* Corrected log file handling:
  * log files are stored in a sub directory named after the service name
  * each back end process now again uses its own log files

* Added variable for service name.

* Added functionality to control the number of possibly active backends by
  manually modifying the variable GRIDFTPD_BACKENDS_NUMBER in the init
  script configuration file:

  Now when increasing or decreasing this value (only do this when the
  daemon is in stopped state!) X back ends are activated. If there is no
  specific configuration file available for the specific backend (e.g. when
  the init script was installed with 4 back ends and now 6 back ends are
  configured), the default back end configuration file is used. Back end
  specific information like port or log file names are configured
  dynamically inside the init script. So the default configuration only
  includes unspecific configuration values.

  It is still possible to deactivate specific back ends by first creating
  a corresponding configuration file (if not existing yet) - see the
  configuration files created during the installiton for naming - and
  making this file non-executable.
Externalized the log file configuration. This is now done dynamically in the init script.