Users: Add "DisplayName"

[HeyJoel]

• Add "DisplayName" field as a more flexible alternative to first/last name. This could be a copy of the username, or a compound name.
• Field will not be required, but we should include an option to automatically copy the username as display name
• Replace username field in UserMicroSummary with display name so that the model does not expose an email address (if used for username).
• Set fname + lname as default value
• Use as name field for Admin area, hide fname/lname
• fname/lname will eventually be removed/migrated to a custom data fields/model when users supports this.

[HeyJoel]

Fixed, will be released in v0.10.

The settings for copying the username to the display name field is "Cofoundry:Users:Username:UseAsDisplayName".