AliTrack etc... storage in AliEvent & co.
Also (Ali4Vector&) casting stmt. in AliVertex::ResetVertices() changed
to make it ANSI compatible for all compilers/platforms.
+09-jul-2001 NvE Support for impact points and user identifier introduced in AliTrack.
+ Also user identifier facility introduced for AliJet and AliVertex.
+12-jul-2001 NvE Memberfunction GetDistance() introduced for AliPosition and support for
+ point of closest approach introduced in AliTrack.
+24-jul-2001 NvE Support for Chi2 and NDF information of track fit introduced in AliTrack.