Log message:
Remove FETCH_USING.
It is a user-defined variable and should NOT be set in Makefiles.

Log message:
Mark packages as not ready for python-3.x where applicable;
either because they themselves are not ready or because a
dependency isn't. This is annotated by
PYTHON_VERSIONS_INCOMPATIBLE=  33 # not yet ported as of x.y.z
or
PYTHON_VERSIONS_INCOMPATIBLE=  33 # py-foo, py-bar
respectively, please use the same style for other packages,
and check during updates.

Use versioned_dependencies.mk where applicable.
Use REPLACE_PYTHON instead of handcoded alternatives, where applicable.
Reorder Makefile sections into standard order, where applicable.

Remove PYTHON_VERSIONS_INCLUDE_3X lines since that will be default
with the next commit.

Whitespace cleanups and other nits corrected, where necessary.

Log message:
Import py27-cxnet-0.3 as wip/py-cxnet.

The cxnet extends IGraph module with some functionality
I am using in higher education.
Some functionality is available with NetworkX module as well.
Function plotting needs matplotlib (pylab).

Functionalities:
- Creating networks with multifractal network generator.
- Creating network from the deb package hierarchy.
- Investigating and plotting degree distribution.
- Graph methods:

 * to list the vertices with most degrees,
 * to plot the neighbours of a vertex.

- A tool to create network evolution models