Head-Rotation Trajectory File: Remove Subframe-Index

The file for the head-rotation trajectory files looks as follows:

0, 1.000000, 0.000000, 0.000000, 0.000000
1, 0.999999, 0.000000, -0.000001, 0.001048
2, 0.999998, 0.000000, -0.000005, 0.002095
3, 0.999995, 0.000000, -0.000012, 0.003143
4, 0.999991, 0.000000, -0.000021, 0.004190
5, 0.999986, 0.000000, -0.000034, 0.005238
...

The first column contains the sub-frame index (corresponding to 5ms subframes), which is basically not used at all on decoder-side (only for a small sanity check). In addition, it makes editing these files more difficult, since the index is expected in increasing order.

I would propose to remove this index from the file-format.