This commit replaces the data members 'nx', 'ny', and 'nz' with a
copy of the GridDims object passed as an argument to the
constructor. In turn, this enables using GridDims::getIJK() to
compute the cell's IJK tuple from its global Cartesian index instead
of implementing the same calculation locally (and incorrectly).
While here, also include the layer index (K) in determining whether
or not a connection is an NNC, and do this just once instead of once
for each MULTREGT record. Cells (I,J,K) and (I,J,K+3) might be
connected across pinched-out layers and for the purposes of MULTREGT
that connection should be treated as an NNC.
f32ff86638