cluster nodes. Not going to try and describe all these changes.

Note that I have not back ported this into the old assign wrapper. We
move inexorably forward.

Worth mentioning:

* Users get VMs only on shared hosts.

* Multiple experiments from multiple projects can share a node.

* Nodes that are acting as shared hosts are in a holding experiment
  and have a tag in the reserved table. All of the links in the
  experiment are tied together in one giant super vlan. We then
  multipleax over that using our standard mechanisms (veths, vlans,
  whatever).

* Lots of complication in the link setup code for dealing with links
  between a virtual node on a shared node, and a private physical
  node. Requires additional vlans and trunking between those
  interfaces. To make life easier, all of the links in the afore
  mentioned super vlan are trunked in dual mode.

* I had to change Mike's code that does the encap determination, since
  openvz nodes cannot do veth encap. I add some new osfeatures
  (veth-ne, veth-en, and vlans).

* On and on and on ...