- base level surface container is now a meshedSurface instead of
a triSurface. This avoid automatic triangulation of surfaces
when they are read, and simplifies the internals.
- sampling types:
* "meshedSurface" (compat: "sampledTriSurfaceMesh")
* "meshedSurfaceNormal" (compat: "sampledTriSurfaceMeshNormal")
- fits better into the general sampling framework, improves flexibilty
and allows code reduction.
ENH: include surface fields on sampledSurfaces that support it
