restapi: cloud-init - rest api for start vm

Support using cloud-init to perform initial setup of virtual machines.

Further details available at:
http://www.ovirt.org/Features/Cloud-Init_Integration

This patch adds support for specifying Cloud-Init configuration when
starting a VM using the REST API.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=990572
Change-Id: I6ad0bfeca23cf8d4b2887010081d63c258032611
Signed-off-by: Greg Padgett <gpadgett@redhat.com>
Signed-off-by: Omer Frenkel <ofrenkel@redhat.com>