message: Improve FaceInfo documentation.
diff: @@ -154,13 +154,19 @@ protected:
  ncmesh.cpp, and pncmesh.cpp files and reverse engineer the code.
  What I found about them so far:
  - Their number is faces_info.Size() - GetNumFaces(), this seems to
  - include a lot of irrelevant uninitialized ghost faces.
  + include a lot of irrelevant uninitialized ghost faces. -> wrong
  + Their number cannot be known without counting them, indeed some ghost
  + faces are included in the non-ghost faces... and most of the indices
  + between `GetNumFaces()` and `faces_info.Size()` are unused. So counting
  + is mandatory.
  - Most of the ghost faces only countains -1 in all their attributes
  (that seems to be explained by pncmesh.cpp:1073-1074).
  The technical documentation below wonders if these are master
  non-conforming faces, I think they're probably just ghost ghost cells,
  unused allocated memory space.
  However, I still tag them as MasterNonConforming in GetFaceInformation
  + -> wrong. I tag them with NA, since they don't seem relevant for
  + anything.
  - They seem to be used as a convenience layer only in NCMesh, why not
  using them all the time?
  - Due to clashing conventions:
  @@ -172,7 +178,11 @@ protected:
  - It seems that ghost faces are only used for shared non-conforming faces
  where elem1 is master and local. I think non-conforming faces where the
  local face is slave are treated through conforming shared faces. (This
  - hack has to be confirmed)
  + hack has to be confirmed) -> Wrong
  + Most ghost non-conforming master faces are wasted memory space, but
  + sometimes they are real ghost non-conforming slave faces...
  + - Ghost faces, contrary to other non-conforming faces also have
  + orientation that is not necessarily 0.
  */
  struct FaceInfo
  {
  