modified:   picostack/templates/instances.html
- Added form.id to fix the problem of multikeyerror.
- Named each action button, so that the corresponding action can be idetified
  and handled by the views.py
modified:   picostack/vm_manager.py
- Corrected number of cores for running kvm command.
modified:   picostack/vms/models.py
- disk_filename is now not a property but a db field. Disk files should not be
  renamed. One should be able to test this for uniqueness. VM renaming still
  leaves the problem of uniqeness of disk filenames on the filesystem.
- custom VmInstance.save() method now set defaults value with
  self.get_default_disk_filename
modified:   picostack/vms/views.py
- Handling actions for save/start/terminate/trash buttons.