- this is a simple container for fields with i-j-k addressing.
It does not support field operations directly, but is primarily
intended to be used when assembling field information with i-j-k
logic. After assembly, the field can be transferred to a regular
field for normal operations. Eg,
IjkField<scalar> assemble({15, 16, 200});
// .. fill in i-j-k fields
Field<scalar> final(std::move(assemble));
assemble.clear(); // be pedantic
...
