Add option for interger serial in SOA record

[unggulzmalqp]

Currently, the serial in the SOA record is using the date format (ddmmyyyyss). Due to way the RESTKnot is designed, it only allows maximal 99 changes per day.

Since there are people that need more than 99 changes per day, I think we should accommodate them. One way to do it is to allow the user to choose integer type in the serial.