fixes #176

Developer dependencies are ~1GB

Cleanup and cosmetic changes.

Fix issue with mountCgroups not recognizing mounted cgroup

Extensibility Improvements

Right now after installing mininet using util/install.sh there is a problem when try to generate doc:
	make doc
	doxygen doc/doxygen.cfg
	make: doxygen: Command not found
	make: *** [doc] Error 127
Adding doxygen, doxypy and texlive-fonts-recommended packages to fix the problem.

s/http:\/\/openflow.org\/mininet/http:\/\/mininet.org/g

Changed mountCgroups to use the file /proc/mounts (instead of the
current case where it uses the less reliable
(http://www.mail-archive.com/lxc-devel@lists.sourceforge.net/msg00455.html)
/etc/mtab thorugh the mount program

fixes #143

Fixes #94

fixes #161

It appears that under certain conditions, such as when a
namespace exits, both ends of a veth pair may get dumped
into the root namespace. We therefore now remove an interface
both from its home namespace and from the root namespace.

This disables slicing by default but fixes bandwidth limits.
Eventually we want to enable both to work together, but for now
this enables one or the other depending on the dpopts setting.

Currently, slicing on the user switch breaks bandwidth limits.
We don't yet have a good way of using both of them at the same time.
I'm inclined to turn off slicing by default, but I have to think
about it and also see if any one is using it...

Fixes another Graph regression relative to NetworkX.

RipL broke because the NetworkX Graph object that was used previously
for topologies is an undirected graph:

>>> import networkx as nx
>>> g=nx.Graph()
>>> g.add_edge(0,1)
>>> g[1]
{0: {}}
>>> g[0]
{1: {}}

There is a separate DiGraph object in NetworkX for directed behavior.

The minimal replacement previously implemented DiGraph behavior.

>>> from mininet.topo import Graph
>>> g2=Graph()
>>> g2.add_edge(0,1)
>>> g2[0]
[1]
>>> g2[1]
[]

This commit restores undirected graph behavior.

Commit 65c35b65 'Remove networkx dependency' broke this line from RipL:

    nodes = [n for n in self.g[name] if self.layer(n) == layer]

To work around this, RipL code would have to be changed to something
like this:

    nodes = [n for n in self.g.data[name] if self.layer(n) == layer]

...which would use an internal variable, data.

It seems cleaner to add this one little feature from NetworkX Graph objects.

If NBEEURL is defined when running install.sh, use that location.

Enables use of a local mirror for netbee download.

Thanks to David Erickson for the code.