wip: [stix2 import] Import of external file observable objects
wip: [stix2 import] Import of external file observable objects

- Support of PE extension to create PE object(s)
  with the corresponding section(s) alongside the
  file object import
- As always with pe and sections, the appropriate
  references are added too

MISP/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,MISP/MISP