Fix #8 - Add fill byte in writeItems

[FiloCara]

This should solve the issue. I did some tests and I was able to write more than 40 boolean variables simultaneously. It still works well while writing integer and real data.

[FiloCara]

The last two commits have been implemented to address the issue of multiple unintended connections being opened with the PLC during network disruptions or when the hardware is under heavy load. This issue has also been impacting the node-red-contrib-s7 node (https://github.com/st-one-io/node-red-contrib-s7/issues/102). In my tests in an industrial environment, the fixes have been successful in eliminating additional unintended connections.