Fix roscore regardless

[furushchev]

• jsk_topic_tools: isMasterAlive was not working correctly.
• jsk_tools: roscore_regardless.py
  • Added feature to pass signals sent to parent to children
  • Set proper attributes on spawn child process
  • Clean and quiet log printing
  • Killing by gradually escalating signals like roslaunch

[mmurooka]

@furushchev
I might heard from you before that some update is necessary in the following use of roscore_regardless (maybe something about respawn?) after this PR is merged, but I forgot that. Do you remember that?
https://github.com/start-jsk/rtmros_hrp2/blob/master/jsk_hrp2_ros_bridge/scripts/hrp2_stat.sh#L13

[furushchev]

@mmurooka Yes, previously a target node is respawned by default, which is now disabled.
If you want to enable respawning target node, I provide an option --respawn or -r for that.