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.

The previous version (12-05-16) does not compile on Ubuntu 12.10.

Also use a local variable to reduce duplication.

Conflicts:

	util/install.sh

closes #100

should fix #128

Try invoking bash processes with -s mininet:host,
for easy identification of hosts. This enables
easy attachment using the util/m script.
closes #121

For local display, allow local root access
For remote display, tunnel with socat/mnexec
This should enable *wireshark in hosts* and fix #119

Signed-off-by: Bob Lantz <rlantz@cs.stanford.edu>