Introduce VeloBackward and track type
Follows LHCb#256 (closed).
Goes with LHCb!3779 (merged) Alignment!314 (merged) Panoramix!122 (merged) and Rec!3122 (merged)
Edited by Andrii Usachov
Follows LHCb#256 (closed).
Goes with LHCb!3779 (merged) Alignment!314 (merged) Panoramix!122 (merged) and Rec!3122 (merged)