[cob_monitoring] enhance topic_status_monitor

[fmessmer]

• fill in hardwareId
• allow to "hz-monitor" several topics (done in #189)
• add rosnode ping functionality (http://answers.ros.org/question/208574/using-rosnodes-api-c/)
• maybe even query which topics are published by a node then generate monitored topics automatically...

@fmessmer FYI

[fmessmer]

not planned