Logging improvment

[Ulrich Dangel]

In order to get useful information the following information should be logged/changed:

• add a state={finished,starting} to the start/stop message
• for the stop message add a duration field as a second + lines field
• put quotes around start_time and end_time
• Introduce a random token in each function toll into log message to uniquely identify them (and make sure they are a field)
• be consistent in the logging