In the Cell/Instance hierarchy, the "terminal" and "leaf cell" concepts
where not clearly defined and partially overlapping. Now, "Terminal" is
the refer to the physical hierarchy (layout) and "TerminalNetlist" to
the logical hierarchy (netlist). The logical hierarchy can be less deep
than the physical one thanks to a Cell dedicated cell flags. Collections
related to the physical hierarchy keep their old names, the one related
to the logical hierarchy are renamed from "Leaf" to "TerminalNetlist".
The name "Leaf" was too ambiguous (leaf for *what* hierarchy).

* Change: In Hurricane::Device, set the "TerminalNetlist" flag once and
    for all. No need set it in all the derived classes again.
* New: In Hurricane::MultiCapacitor, added new parameter "dummy" to
    create dummies around the capacity matrix.
* Change: In Hurricane::Cell, remove "Leaf" related methods, replace
    them by "TerminalNetlist" one, especially Collections. Now we have
    two cl...