Added Summer time (DST) setting. It allows you to apply DST (Daylight saving time) on your device.
Please note that due to lack of DST flag for timestamps in raw data sent from devices, there is no way to clarly parse time in the end of DST period - no way to distinguish time string generated during DST enabled and just after DST end.
Thus messages in that period will be marked with param time.ambiguity.dst: true and time will be parsed without DST. The size of that period will be 1 or 2 hours, according to setting value you set.
