core: infrastructure for VmDevices in next run VM snapshot

Added an infrastructure for including VmDevices in a snapshot
of type 'Next Run'. This should allow enabling/disabling of
devices while VM is running (i.e. similarly to VM properties that
are editable on a non-running VM, a warning message [1] is being
shown upon editing a VM device status).

* Created a new annotation interface for devices:
  'EditableDeviceOnVmStatusField'.
* VmHandler - initialized mUpdateVmsStatic with those fields.
* UpdateVmCommand - passed a list of devices for next run
  when creating the snapshot with new configuration.
* GetVmUpdatesOnNextRunExistsParameters now gets an instance of
  VmManagementParametersBase in ctr [since the new annotation
  (EditableDeviceOnVmStatusField) will be used in this
  parameters file].
* GetVmUpdatesOnNextRunExistsQuery - added a validation for
  updating VM devices.
* Modified client invocations accordingly.

[1] "Some of the changes will be applied after the NEXT RESTART"

Change-Id: I4e7add4e7e09fe8d6d1f93f0d2b96795d838efa2
Bug-Url: https://bugzilla.redhat.com/1035289
Signed-off-by: Daniel Erez <derez@redhat.com>