add optional refresh param for okwstsnow()

Sydney added a similar thing for okwsmstime(). This is basically the same function but returns the time in seconds as a double (down to nanosecond accuracy), instead of in ms as an int. Neither are all that useful without ability to force refresh. I believe this param should actually be turned on by default for these, but we might want to verify that it wouldn't slow any existing code down--for now, keeping refresh=false as default