Unfortunately disabling IPv6 via sysctl doesn't actually
disable it on all of the interfaces by default. Disabling
it via grub disables it entirely in the VM.

Helps with #454

This should help with #393 although it doesn't solve
the root issue of the example failing silently when
vconfig is missing.

Apparently there is a conflict where the lua plugin
conflicts with the built-in dissector for openflow
that is included with 1.12 and up. For now, we will
just not install the plugin. This should fix the
14.10 VM build.

Additionally, I have added a handy function,
version_ge, which compares version numbers in
canonical x.y.z format. Thanks to stackoverflow for
pointing out the incredibly useful sort -V option!

The older wireshark dissectors were not well-maintained
and were a pain to build. They also added tons of extra junk
into our VM images! The ones built into the current
wireshark are deficient for 1.3. The solution for the
future is almost certainly to go with the lua-based plugin,
since it is architecture-independent and should be much
easier to maintain and upgrade.

    This argument expect a parameter which is the version number of OVS you wish to install.
    install.sh -V 2.0.0

    What is nice that I tested, is that you can keep running the above to change
    which OVS version you want to test with.  Also, if a new version of OVS
    is released, just run the above again specifying the new version number.

    The version number must match the version number in the tarball file name
    like openvswitch-2.0.0.tar.gz.  In this case, the version specified
    must be 2.0.0.

fixes #212

fixes #192

Use files instead of sysctl to set limits

fixes #180

D'oh!  Next time test presence _and_ absense of an added env var.

OTOH, when people notice this quickly, it means they're using install.sh :-)

Developer dependencies are ~1GB

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.

Fixes #94

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.