Store correlation

[retostauffer]

As an idea for a future version: Calculate correlation between variables. Our first idea as discussed today with @gabroko is the folowing:

• If there is an AMB T variable for a specific home: Calculate Pearson correlation of all variables of the specific study:home against this one (on all aggregation levels); append a new column in the STAT sheet.
• If there is an AMB T with "home = "ALL" in the config: calculate Pearson correlation of all variables of the same study against this ambient temperature.
• If the config file finds multiple ALL:AMB:T, throw an error when checking the config file.