Add a pointer to the primary context of a connection and use it in all
driver functions that don't dependent on the context type. This includes
almost all functions that deal with a virDomianPtr. Therefore, using
a vpx:// connection allows you to perform all the usual domain related
actions like start, destroy, suspend, resume, dumpxml etc.

Some functions that require an explicitly specified ESX server don't work
yet. This includes the host UUID, the hostname, the general node info, the
max vCPU count and the free memory. Also not working yet are migration and
defining new domains.

This works for file-backed SCSI disk device with a datastore
related source path.

Also don't abuse the disk driver name to specify the SCSI controller
model anymore:

  <driver name='buslogic'/>

Use the newly added model attribute of the controller element for this:

  <controller type='scsi' index='0' model='buslogic'/>

The disk driver name approach is deprecated now, but still works for
backward compatibility reasons.

Update the documentation and tests accordingly.

Fix usage of the words controller and id in the VMX handling code. Use
controller, bus and unit properly.

Allow to specify a proxy to be used by libcurl.

Add a test case and document it.

Extend tests to cover all SCSI controller types and document the
new type.

The lsisas1068 SCSI controller type was added in ESX 4.0. The VMX
parser reports an error when this controller type is present. This
makes virsh dumpxml fail for every domain that uses this controller
type.

This patch fixes this and adds lsisas1068 to the list of accepted
SCSI controller types.

Reported by Jonathan Kelley.

The MAC addresses with 00:50:56 prefix are split into several ranges:

  00:50:56:00:00:00 - 00:50:56:3f:ff:ff  'static' range (manually assigned)
  00:50:56:80:00:00 - 00:50:56:bf:ff:ff  'vpx' range (assigned by a VI Client)

Erroneously the 'vpx' range was assumed to be larger and to occupy the
remaining addresses of the 00:50:56 prefix that are not part of the 'static'
range.

00:50:56 was used as prefix for generated MAC addresses, this is not possible
anymore, because there are gaps in the allowed ranges. Therefore, change the
prefix to 00:0c:29 which is the prefix for auto generated MAC addresses anyway.

Allow arbitrary MAC addresses to be used and set the checkMACAddress VMX option
to false in case the MAC address doesn't fall into any predefined range.

* docs/drvesx.html.in: update website accordingly
* src/esx/esx_driver.c: set the auto generation prefix to 00:0c:29
* src/esx/esx_vmx.c: fix MAC address range handling and allow arbitrary MAC
  addresses
* tests/vmx2xml*, tests/xml2vmx*: add some basic MAC address range tests

* docs/drivers.html.in: list the ESX driver
* docs/drvesx.html.in: the new ESX driver documentation
* docs/hvsupport.html.in: add the ESX driver to the matrix
* docs/index.html.in, docs/sitemap.html.in: list the ESX driver
* src/esx/esx_driver.c: fix and cleanup some comments