Get rid of partial record fields

[dag]

Like affixes. For some shapes, it will result in a runtime error. If instead the field is added to all shapes (possibly wrapped in a Maybe) it would permit adding affixes to shapes that don't have affixes.

A solution might be to not use records and instead write the lenses manually, and use partial lenses for partial fields. Using total lenses wrapped in Maybe might not satisfy the lens laws?

Of this is the right solution it might be useful to add helpers to data-lens-template for automating this.