Modbus plugin: map status of MB transaction onto 2 located BYTE vars (instead of a singlw WORD var).

Modbus plugin: provide user programs feedback on current connection status mapped onto a WORD located variable

Removed harmful assert in ProcessLogger.

ProcessLogger was having an assert in constructor when missing logger, leading to systematic exception when testing options accepted by compiler. This exception was silenced in ProjectController, and then MatIEC was always called without options.