Integrate task kill features into JobScheduler Universal Agent start script

Feature

• JS-1468 specifies how an OS dependent kill is integrated into JUA.
• This requires some enhancements to scripts deployed with JUA:
  • two kill scripts should be provided to kill a process and it's children:
    • for Windows: jobscheduler_agent_kill_task.cmd
    • for Unix: jobscheduler_agent_kill_task.sh
    • Both scripts are located in the ./bin folder of the JUA installation.
  • The kill scripts provide the functionality to kill a task and it's child processes:
    • if the kill script is called with the parameter -kill-agent-task-id=... it
      • finds the process containing that id
      • kills the process including all children
  • The start script starts JUA with the new -kill-script parameter
    • by default the -kill-script is parameterized with the path to the respective kill script for Windows/Unix
    • the environment variable SCHEDULER_KILL_SCRIPT can be used to set a different kill script