rest api: edit running vm

Add field to vm to indicate there is configuration for next run.
Add url parameter for getting the configuration (usage:
api/vms/vmId;next_run)
and the same for updating vm, marking not to hot plug changes if any
(for example not to hot plug cpu if changed while vm is running, usage
is the same)

Feature page: http://www.ovirt.org/Features/Edit_Running_VM
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1072313
Change-Id: I848a9fefb74a982923f655fc1293dc38f419cb1c
Signed-off-by: Omer Frenkel <ofrenkel@redhat.com>