Support preferred locales

[uberfirestone]

Preferred Locales
OPs MUST support requests for preferred languages and scripts for the user interface and for Claims via the ui_locales and claims_locales request parameters, as defined in Section 3.1.2. (Note that the minimum level of support required for these parameters is simply to have their use not result in errors.)

http://openid.net/specs/openid-connect-core-1_0.html#ServerMTI

[rquast]

http://openid.net/specs/openid-connect-core-1_0.html#ClaimsLanguagesAndScripts - claims_locales

These may greatly assist with this hellish task.

https://github.com/mattcg/language-tags
https://github.com/mattcg/language-subtag-registry

[rquast]

#340