Clean up TrackType enum

During the development of v3 tracks, a FittedForward track type was added to the track type enum, as a seemingly temporary solution(?).

By now this is quite confusing, and we should clean up the code such that the pattern recognition algorithm is again explained by the TrackHistory, and the fit status by the FitStatus enums. Note that no algorithms aside from those related to v3 tracks make use of this.