Specifically, refine the representation to allow a boundary condition
to apply to a set of interfaces rather than just a single face. This
support is realised by the introduction of new interface
flow_conditions_append_multi().
Update all consumers of struct FlowBoundaryConditions to accommodate
the one-to-many boundary condition interface mapping in the process.
Specifically, replace the existing flowbc_t (that was densely
represented on each interface, including internal interface and
external no-flow interfaces) with a new structure given by
struct FlowBoundaryConditions
The semantics of this structure mirror those of "struct Wells" from
<opm/core/newwells.h>, but is currently mostly intended for simple,
incompressible flow purposes.
Update pressure solvers supporting boundary conditions to accommodate
the new boundary condition representation in the process.
Andreas Lauser
Atgeirr Flø Rasmussen
Bård Skaflestad