We add a new experimental feature to allow Mininet to run across
a cluster of machines. This is currently implemented via a set
mix-in classes that provide remote nodes that are implemented
via a connection to a remote shell, and remote links which are
tunnels across servers. In this preliminary implementation,
both control and data connections are made via ssh, but this
could change in the future.

A MininetCluster class is provided which allows existing code
to be used with minimal modification - all that is required is
to provide a list of servers to use. A customizable placement
algorithm may also be specified. An experimental CLI subclass
is also provided to make it easier to examine node placement;
status and links commands can also check whether nodes and
tunnels are still running.

Although this is an experimental feature, it does include a
--cluster option to make it convenient to start up a Mininet
simulation over a cluster, and a script to assist with setting
up the prerequisite authentication via ssh key pairs.

The cluster feature is preliminary and missing some obvious
important features, such as parallel startup and multiple tunnel
types, which we hope to add in the future.

file no longer returns image size on 14.04
fixes #373

Fixes #372

Since chroot() doesn't chdir() by default, we are left in
an unreachable directory in node.pexec() (and in xterms.)

fixes #370

Fix output of backgrounded processes

print useful output for tests upon failure

Adding VLANHost to Examples

Adding LinuxRouter to Examples

Fix UserSwitch.connected() as well as testLinkDelay() in test_hifi
We need more than one iteration since the first iteration may show reactive forwarding and ARP delay; currently we have three for good measure, although two is probably enough.

improve startup performance, largely by removing unnecessary ifconfigs

fixes #347

Adding NAT class to NodeLib

Raise exception when link incorrectly formatted

fix for controller shutdown - send SIGHUP rather than SIGKILL

Update to MiniEdit 2.2.0.1

- Replace custom code to set OF protocols with new Mininet available API to set.

Add parameter to set protocol list in OVSSwitch.

- Updated for new Mininet 2.2.0
- Support TCP or SSL for remote controller
- Support HostWithPrivateDirs Hosts

Applying @cdburkard fix to #322

fix Singleton.__call__ error