Add Bfs-spanning-tree algo but kind2 (verify) don't work

test/bfs-spanning-tree/Makefile

test/bfs-spanning-tree/bfs_spanning_tree_oracle.lus

test/bfs-spanning-tree/config.ml

test/bfs-spanning-tree/p.lus

test/bfs-spanning-tree/p.ml

test/bfs-spanning-tree/root.lus

test/bfs-spanning-tree/root.ml

test/bfs-spanning-tree/state.ml

test/bfs-spanning-tree/tree3.dot

test/bfs-spanning-tree/tree3_oracle.lus

test/bfs-spanning-tree/verify.lus