CLOUDSTACK-4760 : Enabling GPU support for XenServer.
CLOUDSTACK-4762 : Enabling VGPU support for XenServer.

This feature is to enable the GPU-passthrough and vGPU functionality,
with the help of this feature, admins/users will be able to leverage
the GPU graphics unit power by deploying a virtul machine with GPU or
vGPU support or by changing the service offering of an existing VM
at any later point of time. There GPU/vGPU enabled VMs are able to run
graphical applications.
For now, this feature is only supported with XenServer hypervisor but
can be extended to add the support of other hypervisors.
CLOUDSTACK-6222: Fix the marvin config generator scripts to include
new syntax changes in marvin code and fix the logFolderPath