Should datashape names/types be mutable/settable?

The current mechanism for changing anything in a datashape seems to be constructing a new string for `dshape` with the needed changes and creating a new datashape. Most of the attributes for important datashape objects like Datashape and Record are defined as properties which cannot be altered. One could try to directly modify the `_parameters` attributes, but that's a pretty ugly hack and `_parameters` is often a tuple of tuples, which is immutable anyway.

With fairly large datashapes where one needs to alter one name or type in a record, it would be much easier to have a method or other way to change the name/type in place rather than having to construct an entirely new `dshape` string to build a new datashape.

This feels like it should be doable, but I'm not sure if allowing Record names/types to be altered has some potential downsides from an architectural perspective that outweigh the benefits.