Creating a bounding box tree for a vector of geometries

Feature request Bounding box tree for a list of geometries without a grid

What does this feature / why does DuMux need it: E.g. to intersect a polyline with a grid or some object where it would be easier to just define the geometries instead of creating a Dune grid.

The bounding box tree is already general enough, it expects a EntitySet which only needs to satisfy a certain subset of the interface of a Dune::GridView. So the task would be to create a new EntitySet class which can be constructed from a vector of geometries instead of from a grid view.