Node placement in volume of original model

[wouterjdb]

Flownet now uses the convex hull of the well nodes as outer border for the placement of new nodes. This means that the newly created voronoi volume distribution (#356) does not always work well as it distributes the volume of the original model. Could we add an option that in the node distribution not the convex hull but the volume of the active cells in the (layer of the) original model is used as boundaries for node placement. This will lead to a more accurate representation of the geometry of the original model.

I think this can also still be defended as "data-driven" as one could get this information from the seismic - just as it was originally done.