WeatherStation: slight update
WeatherStation: slight update

 - Replaced the use of string.find by string.match, as it was not
   working as expected with the new lua interpretor.

 - Slight simplification of extract_value as we now can use a full-blown
   regular expression.

Change-Id: I1d7df66a272120cd10aa40f8e9326057b9709e3d

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi