Multi-value query param should be noun if singular

[pvdbosch]

• Multi-value query param should be singular if noun
• don't set param properties that are already default in example OpenAPI

[pvdbosch]

to check with WG if introducing new guideline (Multi-value query param should be singular if noun) is OK.
Seems to be consistent with examples already present

Example: ?color=blue&color=red vs ?colors=blue&colors=red

Pro: makes more sense when reading URL
Con: singular makes less sense in generated code, e.g. List<String> color

[pvdbosch]

Reviewed by WG, OK to merge