feat(toolbox): add the possibility to xen-command to take on stdin

If only one argument is provided to xen-command (the VM name), then it
read the command to send on its stdin.
Modified the experiment script accorindgly.
feat(toolbox): general improvment of some scripts

Add significants error messages in build-streamcluster and
xen-get-home, and remove useless output.
Make a cleanup in the test partition after the experiment to keep only
the log files in streamcluster-1domu
feat(toolbox): add a script to set memory for xen domains

Add a script to fix the amount of available memory for the given xen
domains.
feat(toolbox): add a script to set the vcpu count for given VM

Add a script to set the count of vcpu for several VM, or reset it to
default.
fix(toolbox): add an error checking to alert when no VM is given

Throw an alert in xen-set-home and xen-set-memory whan no VM name is
given in the argument.
feat(toolbox): add a xen VM pinning script

Add a script to pin VM vcpus on specified phisical cpus