[Feature Request] Add S7 Timer/Counter support

[devaskim]

According to the "Function Block Diagram (FBD) for S7-300 and S7-400 Programming" document, S7 controllers serialized counter/timers payload in specific way (see screenshots below). @xingshuangs Are there any plans to support such data types in S7 client API?

[xingshuangs]

The BCD format data type can be added later.