DumpEventDataToJSON: (slightly) more efficient scheme for track positions
This is a small change to write track positions as [x1,y1,z1,x2,y2,z2 ... ]
instead of [[x1,y1,z1],[x2,y2,z2]...]
. It's a bit less human readable, but is more compact.
This code is not run in production, and only used to dump event data to JSON.