Add scripts for running network experiments

net-eval-setup is a Ruby script that allows the user to specify a
series of network tests by choosing options representing various
types of experiments performed on either an IP or XIA network
stack. The user must explicitly specify which stack(s) to use and
at least one experiment to perform. The number of trials for each
experiment and the time that each experiment runs are also required
parameters.

net-eval-setup creates several temporary files. net-eval-tests is
a temporary file that lists all of the commands required for the
experiments requested. net-eval-status is a temporary file that
lists all required information for a given run of the experiment,
and is updated after each experiment to reflect the information
necessary for the next experiment.

There is an option in net-eval-setup for the experiments to be run
as boot scripts. If enabled, the system will enter a state of
running scripts and restarting the machine for every experiment.

net-eval-run si a Ruby script that uses the information present
in net-eval-status to perform an experiment listed in net-eval-tests.
It sets up the required containers and creates temporary scripts
for them to run. To synchronize the start of the scripts,
net-eval-run creates a temporary file start that reads "1" when
the experiments may begin, and "0" otherwise. The containers
repeatedly check this file to see when they may begin the pw program.

When the experiments have completed, the containers and bridges
are destroyed and the system is rebooted. If the boot script option
was enabled in net-eval-setup, upon rebooting the experiments will
continue running and restarting cyclically.

To better organize the experiments, the temporary files that are
created during the experiments are now placed in a directory
"tmp" which is created the first time that net-eval-setup is run.