[PDF] Preparations for vPDF support

[PDF] Preparations for vPDF support

- extend check-{jinja2,schema}.sh to scan vPDFs and construct
  proper IDF path for vPDFs;
- add support for '/' in PDF fields, by default filtered by j2
  template rendering;

SPEC changes:
- extend remote_management 'type' enum with 'libvirt';

SCHEMA changes:
- add new enum value 'libvirt' according to SPEC update;
- add separate handling of 'remote_management' for baremetal/virtual;
- remote_management 'versions' and 'mac_address' are mandatory for
  all but 'libvirt' (used to be mandatory for all);

Change-Id: Ib3f711cae807c3ab27920391402ba74844f155c3
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>