core,ui: Unicode support for description fields in OVF

Adjusted validations to accept Unicode characters in the
following fields: VM/Template description, Snapshot description
and Disk description/alias.

* VmBase/CreateAllSnapshotsFromVmParameters:
  use ValidDescription annotation for description field.
* ValidDescription:
  use ValidationUtils.ONLY_I18N_ASCII_OR_NONE as regexp.
* BaseDisk: use ValidI18NName annotation for alias field.
* correlated the UI models to use the same validations.
* modified AppErros accordingly.

Change-Id: Ia03cc8f1a938997fa6d38e90bf4ac4781307d8aa
Bug-Url: https://bugzilla.redhat.com/885373
Signed-off-by: Daniel Erez <derez@redhat.com>