Merge branch 'dev'
Merge branch 'dev'

* dev: (76 commits)
  add the creating user as a member to the group
  updated schema
  removed measurement.modify media type
  added fixme
  seperated measurement time and creation time
  identifier in track list
  custom media types for sensors and phenomenons
  restructured track provider
  replaced users by user
  include measurement indentifier in JSON
  measurements provider
  identifier for measurements
  index for bbox
  license header
  measurement provider
  sensors provider
  phenomenons provider
  phenomenon provider
  deparameterized measurement value
  license headers
  ...