Add support for VirtualBox 4.2 APIs

Add support for VirtualBox 4.2 APIs

A few things have changed in the VirtualBox API - some small
(capitalizations of things in function names like Ip to IP
and Dhcp to DHCP) and some much larger (FindMedium is superceded
by OpenMedium). The biggest change for the sake of this patch
is the signature of CreateMachine is quite a bit different. Using
the Oracle source as a guide, to spin up a VM with a given UUID,
it looks like a text flag has to be passed in a new argument to
CreateMachine. This flag is built in the VirtualBox 4.2 specific
ifdefs and is kind of ugly but works. Additionally, there is now
(unused) VM groups support in CreateMachine and the previous
'osTypeId' arg is currently set to nsnull as in the Oracle code.

The FindMedium to OpenMedium changes were more straightforward
and are pretty clear. The rest of the vbox template changes are
basically spelling/capitalization changes from the looks of things.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>