KeptFieldSet

One kept field set: the fields of an earlier solve, which a field reference names as `<hash>/<field>` (field-presentation §FVD-6, §FVK-7).

In the namespace field. Declared in src/libs/libfield/field/KeptFieldSets.hpp.

Detailed description

It holds its mesh, so a field of it transfers onto another mesh through the point locator and the interpolation of the sampler (§FVS-1). The set and the mesh do not change after the load.