Add support for the existing behaviour (where each open boundary could be given a common sponge coefficient for all its nodes) and Rory's addition where every node in a boundary can be given both varying radius and coefficient at each node.
Add support for the existing behaviour (where each open boundary could be given a common sponge coefficient for all its nodes) and Rory's addition where every node in a boundary can be given both varying radius and coefficient at each node.

pwcazenave/fvcom-toolbox,pwcazenave/fvcom-toolbox