Suppress version strings on properties or values from external schema references

[jautor]

The doc generator adds a notation showing the "version added" for any property or enumeration value after v1.0.

But when the property or enum values are defined in another schema, and included by reference, that version information is confusing - because it is based on the version added in the referenced schema, not in the current schema.

The simplest fix here is to suppress the version added string when properties or enum values are defined externally. The deprecation version should also be suppressed, but the "deprecated" notation and the reason text should be retained.