Spline geometries for isogeometric analysis

Isogeometric analysis is a finite element technique that allows to solve partial differential equations defined on spline surfaces. This is useful because a lot of geometries used in engineering are directly available in this format, and the grid generation step can be skipped. However, no Dune grid implementation is currently able to represent spline geometries. The goal of this project is to develop such a grid manager for the special case of spline surfaces representable as a single tensor-product patch.