Races during safety delay.

[klaudiusz223]

If shutters are in safety delay period invoking setLevel() and stop() before safety delay finished doesn't stop shutters. Stop is ignored. 2nd issue. In my opinion safety delay should not be taking into consideration when direction is not changed. Now safety delay is always checked even when direction in previous move was the same. Another small improvements with safety daley is possibilty of defining SAFETY_DELAY without library source code modification. For example 77c686528032a4d5cc26aca05cf69d6732b9a7df