This commit adds the DuplicateNodes property to the structured
RCB partitioners, which controls where the nodes between
partition interfaces will be duplicated or not. By default the
nodes are duplicated, which yields partitions that are abbuting
at the interfaces sharing a face. If the DuplicateNodes property
is switched off, there will be a "gap" between partitions, which
is common with Finite Difference codes in particular.

Change-Id: If57529e60f608444dbd055d62d1b1d863e22b924