New S3 A/B Harmonisation

Because of the tandem phase of S3 A/B it is possible to harmonise both sensors.
This has been documented in two papers:

• OLCI A/B Tandem Phase Analysis, Part 1: Level 1 Homogenisation and Harmonisation

• OLCI A/B Tandem Phase Analysis, Part 2: Benefits of Sensors Harmonisation for Level 2 Products

BC experimentally implemented this as GPF graph. This shall be now turned into a usable operator.