Add zabbix[preprocessing_queue] to Template App Zabbix Server

new item zabbix[preprocessing_queue] should be added to the default zabbix template:
https://www.zabbix.com/documentation/3.4/manual/config/items/itemtypes/internal

Todo:

• add item
• do not add trigger (use preprocessing worker/manager busy item)
• add graph of queue and add it to host screen
• update template in svn/share.zabbix.com/zabbix.org