replace include_leaves option in InitializeWeftEdges

[Max Eschenbach]

include_leaves is not useful as an option. instead something like force_cast_on and force_cast_off should be implemented.
force_cast_on > connects all nodes at pos index 1 to one another (like a second row of leaf nodes at the start)
force_cast_off > connects all nodes at pos index -2 to one another (like a second row of leaf nodes at the end)