WIP oauthclient/accounts: permanent login support

* Sets session.permanent when then user marks 'remember me'.

* Allows configuration of oauth login to set if session should
  be permanent.

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
We could maybe do it through the oauth login url by adding`&permanent=1`. It should be also configurable per client.

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PS: If we keep it please add dot at the end ;)