Hyper-V Adds support for RemoteFX

OpenStack VDI support on Hyper-V can greatly benefit from enabling RemoteFX
in the Nova driver.

RemoteFX allows a guest VM to access the hypervisor's GPU features for 3D
graphical acceleration.

Guest configuration is performed by specifying the number of virtual desktops
to be used by the VM and the maximum resolution, with a given set of predefined
values:

"1024x768"
"1280x1024"
"1600x1200"
"1920x1200"
"2560x1600"

The hypervisor available resources include the total video memory provided by
the combined video adapters configured for RemoteFX.

The RemoteFX resources are provided by the hypervisor and need to be handled
in a way similar to other compute resources. In particular:

* The Nova Hyper-V driver needs to report the amount of available RemoteFX
  video memory as part of the host capabilities
* The Nova Hyper-V driver needs to evaluate video memory requirements specified
  in the flavor extra specs when spawning images
* The Nova scheduler needs a filter to allocate instances based on video memory
  flavor requirements. The filter needs also to be taken into account for live
  migration / cold migration / resize operations.

Example flavor with RemoteFx support:

    nova flavor-key remotefx1 set "hyperv:remotefx=1280x1024,2"

The amount of video memory consumed by an instance based on a given resolution
and monitor count can be calculated as:

video_memory = 64*horizontal_res*vertical_res*monitor_count
e.g.: 64*1280*1024*2 = 167772160 bytes

During the configuration of Hyper-V instances, RemoteFX resources can be
assigned by using the Msvm_Synthetic3DDisplayControllerSettingData WMI class.

On each compute host, the "Remote Desktop Services Virtualization Host" (RDVH)
role must be enabled on the host and one or more physical GPUs with RemoteFX
support need to be available.

RDVH can be enabled with:

    Add-WindowsFeature –Name RDS-Virtualization