Definitions of requirement, recommendation and permission

[heidivanparys]

The definitions of “requirement”, “recommendation” and “permission” should be harmonized with the definitions in the latest ISO/IEC Directives, see https://www.iso.org/sites/directives/current/part2/index.xhtml#_idTextAnchor007

It seems that the definitions of "requirement" and “recommendation” in the ModSpec are based on an older version of those Directives.

[cnreediii]

@heidivanparys Not sure about that. Need to discuss. Thanks