implementation of IDP renew transaction

[Alexander-Kreutz]

No description provided.

[qligier]

angular-oauth2-oidc uses the same URL for the token retrieval and the token refresh, simply changing the grant_type, and offers no possibility to change it.
I'm not sure if it's specified by OAuth2; in doubt, I merged both routes (/token and /renew).

When refreshing the token, we need to specify the IDP (/token/alias/hin); it's not needed for the token retrieval but is still supported (the alias is simply ignored). When the OAuth library uses the same URL, it has to be specified.

I still need to implement the support for all IDPs.

[qligier]

I implemented the multi-IDP support in the renew and could test it with TrustID.
For me, the PR is ready to merge.