Operable declaration refactored.

Specifically, :list.set_to_string() has been shifted to
={*-main/var/list/set/string} and all existing functions in such parcel
refactored so as to defer to such function (rather than substantially hackier
eval() invocations).

"And all was modestly right with the world,
 Defrayed of its frockless glee,
 Distemperately,
 As it was."