Merge pull request #21 from fanf/bug_3949/Update_ldap_authentication_documentation

Fixes #3949: Update LDAP authentication procedure
Revert "Fixes #3949: Update LDAP authentication procedure"

This reverts commit 880fc6485c29489b3cc8a8eb82ed00fab8bfa385.
Fixes #3829: document LDAP authentication mixed with rudder-users.xml defined authorization