Rename the the meaning for shut as whats used in Eclipse.
STOP: Well stopped off above the formation. I.e. allow for flow in the
well.
SHUT: Well completely isolated from the formation. The well is removed
from the well list.
New function well_controls_clone(), implemented in terms of the
public API only, mirrors the objective of function clone_wells(),
only for well control sets. Add a basic test to demonstrate the
function too.
