Revise logging

[zven]

Aims of logging / Why do we do this?:

• ensure participation after study -> kick out participants that did not use the app
• ensure that app has worked properly -> location updates
• analyze behavioural component: how often have users actually paused the tracking within the app

Current issues:

• very long csv file -> hard to see what happens where
• logging of some events does not work
• timestamps hard to read / screwed up

Ideas:

• introduce prefix for interesting events that can be easily analyzed / searched for via script
• fix timestamps
• write small python script that analyzes logs for
  • location updates per day
  • computed inferences
  • open of map and diary