Implement Catmull-Rom Interpolator

[gwlucastrig]

The core gridfour module includes a 2D grid-based interpolation class using the B-Spline curve fitting algorithm. There would be advantages to implementing a companion interpolation class based on the Catmull-Rom interpolation method.

A new class should implement the interface IRasterInterpolator.

As a reminder, the current policy for the gridfour core module is that it not have any external dependencies on 3rd-party APIs other than the standard Java API. While we may be willing to yield a bit on this rule in the future, implementations would need to make a convincing case for doing so.