Show a user's login methods on the user details page in the admin area

We have had a few people who can't login because they originally used a provider (e.g. GitHub), but are then trying to log in via another mechanism. This change shows a user's available login methods in the admin section, so we can easily point them in the right direction.
I've had a go at doing this. Ultimately, somewhere you need to map between the provider name and the display properties (e.g. name, css icon). See what you think:

https://github.com/adrianbanks/dddeastanglia/commit/9b8a4717085281a6b73149df1d235e37b68af1e7