User actions not working for chained entity provider

[szymach]

If you define a chain provider for login form with at least two entities not having the same table, only the class defined in the fsi_admin_security.model.user parameter will be checked against the provided credentials. Obviously this should be changed, so all defined entities will be checked against.

Example - ChangePasswordController.

[szymach]

Proposed solution - change fsi_admin_security.model.user to an array and check each defined entity.

UPDATE This will require a lot more work and is postponed until 3.0 or later.