[BuildingServer] merge "Next" branch. Delete 3DTiles branch

[EricBoix]

BuildingServer stale branches must be cleaned-up:

• next branch corresponds to a part of Jeremy Gaillard's Phd and concerns dynamic rule prescribed 3DTiles generation. This feature should be maintained and ported on top of a recent py3DTiles version.
• 3dTiles branch seems to be a Tiler code realized by Jeremy Gaillard for Oslandia. More recent versions, strongly inspired by this branch, of such Tilers have been realized on top of py3DTiles. Unless Oslandia decides to rebase this code on Py3dTiles, this branch should probably deleted.

References

• Above information is a synthesis of email exchanges between Jeremy Gaillard and Eric Boix as of July 2019.
• This issue is a follow-up of #54

[DiegoVinasco]

@EricBoix bump

Est-ce que je peux fermer ces branches ?