* Router shutdown:

    - Fix failsafe shutdown hook broken in 0.8.8;
      HUP, INT, and TERM signals should now shut down cleanly.
    - Shutdown hook no longer prevents other hooks from running
    - Trap HUP, if router.gracefulHUP=true, and do graceful shutdown.
      Only under wrapper, non-Windows.
    - i2prouter stop now uses SIGTERM
    - Implement i2prouter graceful using SIGHUP (ticket #580)
    - Configure wrapper to ignore SIGUSR1 and SIGUSR2 as they will shut down
      or crash the JVM