Enables VLAN Networking for Nova cookbooks

* Parameterizes the necessary nova.conf options to enable
  VLAN networking properly with the cookbooks
* Modifies the way nova-manage network create is called
  in recipes/nova-setup.rb to accomodate not having
  any networks and having networks that have no dns
  and that have a vlan key
* Major update to the README to correct all the outdated
  attribute information and add some background on how
  the service endpoints are configured and the networking
  works

Addresses:

  mattray/nova Issue #5
  mattray/nova Issue #3