Standardize OCSF mapping rules format

[Res260]

The ocsf.py file implements a non-standard mapping rule definition. Since Crowdstrike is a contributor to OCSF, and the YAML-based approach is way better than using JSON to define mapping rules to translate to OCSF, it would be a good opportunity to standardize this format to be used to translate anything to OCSF, not just FDR.

See this discussion for details.