Change per tree BSF indexing by global BSF indexing.

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
Change the indexing of HyperTree and remove dead code & vars.

HT are now indexed in such a way that there is no more
dead index.
HTGSource in quadric mode use the GlobalIndexStart mode to
avoid the storage of the local to global node id per tree
(contrary to descriptor/mask sources which use a BSF global
indexing mode, quadric nodes are numberered on a per-tree
basis).

Also remove some no more used functions and vars.

Change-Id: Ie5fe5f267a22706334d883d330b8aa9bbb3926e2
Merge topic 'Enh-HTG-Add-BSF-GlobalIndexingMode' into master

a45a52a1 Change the indexing of HyperTree and remove dead code & vars.
c5873cf4 Change per tree BSF indexing by global BSF indexing.