Distinguishing successful TAG lens interpolation from failed interpolation

[liorgolgher]

When TAG lens interpolation fails, the data matrix is collapsed along the axial dimension. While this solution is helpful for debug, it can complicate downstream analysis pipeline that expects the data matrix to include the axial dimension. Please allocate a distinct matrix in the resulting HDF5 for the collapsed matrix.

This request is relevant, of course, only for version 1.0 (#13).

Thanks!