Summary of changes:

Summary of changes:
- Change sign of deflection length (previously inconsistent with TRAP  model,
  to be clarified which one is used in reality)
- decrease windows for track matching, possible due to better tracklet  parameters
- Change handling of output tree (not owned by current directory after  creation)
- check for a = 0 in pt-calculation
- added GetLabel to AliTRDtrackletGTU
- change CookLabel according to other changes (offset of 1 in label)