Zabbix

.........T [ZBXNEXT-8558] added MantisBT webhook

* commit '4b830686ea8c4fe8e3bd1788129a1f4c52642d46':
  .........T [ZBXNEXT-8558] removed unnecessary header
  .........T [ZBXNEXT-8558] fixed error message formatting
  .........T [ZBXNEXT-8558] fixed reviewers remarks and proof reading
  .........T [ZBXNEXT-8558] updated readme and added few images (abiba)
  .........T [ZBXNEXT-8558] update Mantis BT readme (abiba)
  .........T [ZBXNEXT-8558] added MantisBT webhook (abiba)