This global breadth-first search let the user access to point
data in the same order as in the descriptor which describes
the tree representation in BFS.
Moreover, each tree node (even non-leaf ones) can now have
data attached. As previously, the dual only address the tree
leaves.
Updating source, filters and tests to take advantage of this
new behaviour.

Change-Id: I4998336e38cc2d5cf79ec50e51ecc877cb74077e