Reading / Writing of basic types PLC S7.

The reading / writing of the basic S7 data types is corrected. In this version it focuses on the S7-300 and S7-400 devices.
It also corrects the handling of arrangements associated with the basic types.

In the case of complex variables of type time (DATE, TIME, TIME__OF_DAY, etc.), since there is no direct equivalence in Java, its conversion is left at the user application level.