Elevated Session State : Add support for a confirmation without password

[michaellwest]

This could be a good solution for the following scenarios:

• Using Federated Authentication
• Tired of entering a password but still want the confirmation

[michaellwest]

Using ElevationAction.Password produces the following dialog:

Using ElevationAction.Confirm produces the following dialog:

[michaellwest]

This could help #1102 @dmborel @mitchclemens