New function that finds the closest structure form a point +
revised other structure search functions
Some consistent renaming and cleanup
Small fixes
Use new search function to find daughter disk
Make sure get_neighbor_surfaces does correctly filter out the
structures on the ignore list
Ignore closest cylinder and check whether it is located correctly
when constructing Cyl.SufracePlanarSurfaceInterfaceSingle

Remember this is actually an Interaction!
Fix ignore lists in check_domain()

TODO This should be somehow unified with the ignore lists defined
by the shells one day.
Clean up single_reaction behavior for Cyl.SurfacePlanarSurfaceInterfaceSingle

Now that the interface particle is located on a disk which is a substructure
of the plane the unbinding should not require any special treatment, but just
follow the same routine as for the cylinder and cylinder cap unbinding.
Put MixedPair1DStatic on correct ignore list in check_domain()
Revise domains for Cyl.Surface->PlanarSurface transfer

- Rename Cyl.SurfacePlanarSurfaceInterface -> Cyl.SurfacePlanarSurfaceIntermediate

- Newly defined Cyl.SurfacePlanarSurfaceInterfacetestShell, which now is actually
  derived from DiskSurfaceSingletestShell

- Modified DiskSurfaceSingletestShell and DiskSurfaceSingle to carry a custom
  structure ignore list

- Updated switchbox for creation of the modified domains in egfrd.py

- Updated make_new_domain() to deal with custom structure ignore list

- Updated ignore lists in check_domain()
Some cleanup of deprecated stuff
Fixes to make MixedPair1DStatic work with the new interface situation
PlanarSurfaceCylindricalSurfaceInteraction -> PlanarSurfaceDiskSurfaceInteraction
+ some necessary changes to adapt to new way of Cylinder->Plane transfer
New testShell type MixedPair2DStatictestShell, which is for making a
PlanarSurfacePair with a static particle on a (sub)disk
Minor fixes