The Open Nebula driver has been unmaintained since it was first
introduced. The only commits have been for tree-wide cleanups.
It also has a major design flaw, in that it only knows about guests
that it has created itself, which makes it of very limited use.

Discussions wrt evolution of the VMWare ESX driver, concluded that
it should limit itself to single-node ESX operation and not try to
manage the multi-node architecture of VirtualCenter. Open Nebula
is a cluster like Virtual Center, not a single node system, so
the same reasoning applies.

The DeltaCloud project includes an Open Nebula driver and is a much
better fit architecturally, since it is explicitly targetting the
distributed multihost cluster scenario.

Thus this patch deletes the libvirt Open Nebula driver with the
recommendation that people use DeltaCloud for managing it instead.

* configure.ac: Remove probe for xmlrpc & --with-one arg
* daemon/Makefile.am, daemon/libvirtd.c, src/Makefile.am: Remove
  ONE driver build
* src/opennebula/one_client.c, src/opennebula/one_client.h,
  src/opennebula/one_conf.c, src/opennebula/one_conf.h,
  src/opennebula/one_driver.c, src/opennebula/one_driver.c: Delete
  files
* autobuild.sh, libvirt.spec.in, mingw32-libvirt.spec.in: Remove
  build rules for Open Nebula
* docs/drivers.html.in, docs/sitemap.html.in: Remove reference
  to OpenNebula
* docs/drvone.html.in: Delete file