Update ds18b20 and move ds18b20 and sht20 into modules folder

guowenxue

2018-10-14 0007a0beea36408539e623d742787c38c03b5c80

tools/rpi_crosstool.tar.bz2 does not exist in tree e0aa301ad2c54e26004151b73346fe0f96ec439e