Merge branch 'master' into dev

* master:
begin and end time for tracks
temporal filter classes
temporal filtering of tracks and measurements
removed unused field
parsing of temporal filter queries (fixes #94)
license headers
Merge branch 'time' into dev

* time:
  license headers
  parsing of temporal filter queries (fixes #94)
  removed unused field
  temporal filtering of tracks and measurements
  temporal filter classes
  begin and end time for tracks
Merge branch 'dev'

* dev:
  license headers
  parsing of temporal filter queries (fixes #94)
  removed unused field
  temporal filtering of tracks and measurements
  temporal filter classes
  begin and end time for tracks