restapi: clone vm

REST API part of the clone VM:
- added new action: 'clone'
- contains a parameter 'vm' where the type is VM
 - only the 'name' is used from this VM, but used the VM for simple extensebility in the future

Change-Id: I18cb01dc83f0a57a7a572fa0da0c7e3397c43707
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1058832
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>