DEFEATURE: remove surfMesh samplers - superseded by sampledSurfaces

- this functionality was originally added to allow sampling of volume
  fields onto a surface in order to perform calculations on them.

  However, the sampling framework essentially mirrored the
  sampledSurface, but was less complete.

  It is now possible to store sampled surfaces on a registry and
  do calculation with their fields. This is the preferred method,
  and thus removing the surfMeshSample duplicate code.