[WFLY-2848] A new option to allow the users username to be re-loaded from LDAP in the management realms.

By default we use the username supplied by the user, this pull request allows us to re-load the username from LDAP.  This covers a couple of scenarios: -
 - Log in with an e-mail address and switch to a username.
 - Correcting the case of the username.

This pull request should only be merged after: -
  https://github.com/wildfly/wildfly/pull/5876

And even then it is only the last commit is required.

As with the LDAP cache pull request no critical need for WildFly 8 just would be nice to get it in - porting over to version 3 of the management schema in WildFly 9 would not be an issue.