Merge branch 'datamodel' into event-stream

* datamodel:
  fixed get track by id
  basic tracks provider implementation
  added missing exception mappers to provider module
  added track identifier
  removed collection name for embedded class
  rest track
  core + mongo modules updated
  measurement module added to mongomodule
  measurement validator + updater (init)
  license header updates
  validator / updater for track
  REST REST and more REST
  rest + core changes for measurement
  rest things
adding of measurements to track