[Feature]: Allow returning YAML instead of json

[mdornseif]

Is your feature request related to a problem? Please describe.
I have to parse responses with a very minimal pattern matching engine on embedded hardware. JSON is hard to parse with that. YAML would be much easier to match.

Describe the solution you'd like
Allow http://ipaddress:8087/objects?pattern=system.adapter.admin.0.*&yaml which would return a YAML document instead of a JSON document.

Describe alternatives you've considered
Building a JSON-to-YAML proxy.

[Apollon77]

Sorry but yaml is no standard in API communicationm just for config files ...