Rework item local numbers in their sub-items

All possible values are now filled using adequate types.

For instance in 1d, since nodes, edges and faces designate the same
entities, the following values are defined: nodes<->cells,
edges<->cells and faces<->cells. Actually, in that case, the same
memory (embedded Array) is used for all these data.

In 2d, only faces and edges share the same data.