Rewrite of workout file processing [in progress]

[SamR1]

Different steps for the rewrite, in order to improve performances and allow some next features implementation:

• [x] Part 1 (https://github.com/SamR1/FitTrackee/issues/194, released in v0.10)
  • rewrite workout creation
  • add asynchronous archive import
  • handle other file formats: .fit, .kml/.kmz, .tcx
• [x] Part 2 (https://github.com/SamR1/FitTrackee/issues/810, released in v1.0)
  • store file data in database
    • workout starting point geometry
    • segment geometry
    • segment points with all data (coordinates, elevation, speed, HR...)
  • add uuid and start_date to WorkoutSegment table
• [ ] Part 3 (https://github.com/SamR1/FitTrackee/issues/952)
  • remove unnecessary storage of generated GPX file when the file extension is not .gpx (and add GPX generation on file download). The original file is still stored to allow data refresh.
  • use uuid instead of WorkoutSegment composite primary key (workout_id, segment_id)
  • remove methods based on gpx file to get chart data and to display map