Fix difference between draft and spec

[TcM1911]

Addressing things reported in issue #27.

Changes:

• identity_class changed to optional
• indicator_types changed to optional
• infrastructure_types changed to optional
• malware_types changed to optional
• os_execution_envs changed to operating_system_refs
• report_types changed to optional
• threat_actor_types change to optional
• tool_types changed to optional
• parent_directory_ref added to file hash contribution

[codecov[bot]]

Codecov Report

Merging #28 into master will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #28      +/-   ##
==========================================
+ Coverage   95.68%   95.70%   +0.01%     
==========================================
  Files          41       41              
  Lines        3708     3725      +17     
==========================================
+ Hits         3548     3565      +17     
  Misses         80       80              
  Partials       80       80              

Impacted Files	Coverage Δ
file.go	90.29% <100.00%> (+0.19%)	:arrow_up:
identity.go	100.00% <100.00%> (ø)
indicator.go	100.00% <100.00%> (ø)
infrastructure.go	100.00% <100.00%> (ø)
malware.go	100.00% <100.00%> (ø)
report.go	100.00% <100.00%> (ø)
threat-actor.go	100.00% <100.00%> (ø)
tool.go	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 59d9d03...37d5fb7. Read the comment docs.