Reading data from CSV reports results in invalid JSON report data

Reading data from CSV reports results in invalid JSON report data if report contains additional attributes like YOP.

When converting CSV to JSON, multiple CSV lines need to be merged into a single reportItem.
The decision which item to merge into is currently made only on the itemID attribute. This needs to be widened to all available attributes. Otherwise multiple entries with the same itemID but different YOP 's get merged into the same reportItem.

The function for merging multiple months also needs to be adjusted.