fixed bug which caused too many '???' to be appended. Bug should not have caused data to be corrupted
added some checks to avoid illegally formatted data to be saved
rewrote houseprint so all sensor data is pulled from google using 1 query instead of multiple, resulting in a big speedup in script execution time
bugfix in last commit
Houseprint.get_sensor() returns None when there is not sensordata for the given sensor