Make Active Directory password and Active Directory User DN fields non-mandatory

[CamiAndrei]

Currently the Active Directory password is mandatory.
Steps to reproduce:

• Add Connection details
  • Active Directory server address
  • Active Directory server port
• DO NOT click Check Connection
• Click Save

Results: The Active Directory password and Active Directory User DN are required.

However if you then click Check connection the connection is successful.
The Check connection saved information going over the mandatory fields check.

The anonymous access to the server is allowed as documented in: https://store.xwiki.com/xwiki/bin/view/Extension/ActiveDirectoryApplication -> Connection settings section and https://extensions.xwiki.org/xwiki/bin/view/Extension/LDAP/Authenticator/#HGenericLDAPconfiguration -> configuration in the xwiki.cfg .