Performance Improvement - Replace classes used for data storage by named tuples

[Fabien]

The following class are used only to store data. The performance and the memory footprint should be better if those classes are replaced by named tuples.

class Vertex:
    X = 0.0
    Y = 0.0
    def __init__(self,x,y):
        self.X = x
        self.Y = y

class Edge:
    start = -1
    end = -1
    is_primary = False
    is_linear = False
    cell = -1
    twin = -1

    def __init__(self, start, end, cell, twin):
        self.start = start
        self.end = end
        self.cell = cell
        self.twin = twin

class Cell:
    cell_identifier = -1
    site = -1
    contains_point = False
    contains_segment = False
    is_open = False

    vertices = []
    edges = []

    source_category = None

    def __init__(self, cell_identifier, site, vertices, edges, source_category):
        self.cell_identifier = cell_identifier
        self.site = site
        self.source_category = source_category
        self.vertices = vertices
        self.edges = edges
        if len(self.vertices) > 0:
            self.vertices.append(self.vertices[0])