Moved well_controls implementation to separate file well_controls.c.
Removed struct WellControlManagement and replaced with simple integer field cpty in the WellControls structure.
Removed #include <opm/core/well_controls.h> from wells.h and inserted explicit #include <opm/core/well_controls.h> where needed.
Added well_controls_get_xxx() and well_controls_set_xxx() functions. The well_controls_reserved() function is called from well_controls_add() and not explicitly.
Reimplemnted struct WellControls access to use the set/get functions in well_controls.c
Temporarily added symbol HAVE_WELLCONTROLS before including well_controls.h - to get acces to the internal elements in struct WellControls.