Refactor the sidebar to use Django templates
With this change the html for the sidebar is no longer generated by
Melange, instead it's delegated to Django (which is what it does
best anyway). The downside is that it is no longer possible to have
arbitrary deeply nested menu's.
# Until model subclassing is a possibility, a mixin class is used to add
# the necessary functions that may be contributed for geographic objects.
class GeoMixin:
"""
The Geographic Mixin class provides routines for geographic objects,
however, it is no longer necessary, since all of its previous functions
may now be accessed via the GeometryProxy. This mixin is only provided
for backwards-compatibility purposes, and will be eventually removed
(unless the need arises again).
"""
pass