Add pybind11 interface for Point2DList and relatives

Due to time constraints, Point2DList is originally being implemented as a C++-only class emulating STL lists. A python interface should be added when feasible.

Using pybind11, it would be relatively easy to make Point2DList behave similarly to a standard Python list; conversely, using swig to wrap the class's very C++-like interface would be difficult and is best avoided.