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[ZBXNEXT-2289] implemented multiple LDAP servers support

* commit 'a0ad56fa90366187ff92a311596eb7d9a9508d97':
  [ZBXNEXT-2289] fixed note for ldaps protocol
  [ZBXNEXT-2289] added missing changes; fixed wording and example style
  [ZBXNEXT-2289] minor changes
  [ZBXNEXT-2289] fixed api changes page
  [ZBXNEXT-2289] changes 6.0 to 6.2 updated
  [ZBXNEXT-2289] userdirectory changes; authentication changes
  [ZBXNEXT-2289] added userdirectory: update, create, test; minor fix in authentication
  [ZBXNEXT-2289] usergroup changes; authentication changes; initial userdirectory changes, incomplete