Introduce a new section memorytune to support memory bandwidth allocation.
This is consistent with existing cachetune. As the example:
below:
  <cputune>
    ......
    <memorytune vcpus='0'>
      <node id='0' bandwidth='30'/>
    </memorytune>
  </cputune>

vpus      --- vpus subjected to this memory bandwidth.
id        --- on which node memory bandwidth to be set.
bandwidth --- the memory bandwidth percent to set.
Signed-off-by: NBing Niu <bing.niu@intel.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>