Fixed issue where using the 'bin()' operation did not correctly create a
'<variable>_weight' variable from a 'weight' variable when it was missing.
Added default units to documention on variable name conventions.
Updates to product ingestions:
- Calipso L2: fixed unit of backscatter coefficient
- ERS GOME L2: fixed unit of cloud top height
- S5P L2 AER_LH: fixed unit of aerosol optical depth
- S5P L2 SO2: add scaled avk for 1km/7km/15km box profiles