ConcatDiskArray could be deleted

[felixcremer]

Now that there is a ConcatDiskArray in DiskArrays there is no need for DiskArrayStack in DAT. We should remove it to reduce confusion.
I am not sure, what are the actual differences between the two types.

[meggart]

It is actually ConcatDiskArray which is the equivalent one. DiskArrayStack stacks arrays along a new dimension while ConcatDiskArray concatenates along an existing one.

[felixcremer]

Ok, so the question is, whether we can and should move DiskArrayStack to DiskArrays