[META 319] Add sanitize_field_names to remote config

[basepi]

Spec: elastic/apm#334
Meta: elastic/apm#319

Default should be:

password, passwd, pwd, secret, *key, *token*, *session*, *credit*, *card*, authorization, set-cookie

Note that the implementation of this also includes adding the option to Kibana.

• Implemented
• Added to Kibana
• Released (breaking, 6.0)