LDAP Wizard: keep Base DN always visible
LDAP Wizard: improve check for Agent DN and Credentials
LDAP Wizard: determine port without credentials. don't hide the port input field
LDAP Wizard: remove ugly whitespace where it should not be
LDAP Wizard: make UI behaviour more consistent and more pleasant when determining Base DN
Merge pull request #5809 from owncloud/fix5753

LDAP Wizard: proper behaviour with anonymous bind, fixes #5753