Basic export of users from the user manager

[SimonAnnetts]

Ability to export a list of users from the user manager. Basic attributes:

Firstname, Surname, Display Name, Email Address, Created Date.

[SimonAnnetts]

Has to be done in tandem with cloudscribe.UserProperties.KVP as this replaces the index.cshtml useradmin view.

cloudscribe/cloudscribe.UserProperties.Kvp#55

[SimonAnnetts]

The client paying for this now also wants the User ID field included. This is a GUID.