Fix sign in offset for scaling and selection of reference bands for Landsat

[lukasValentin]

The sign of the offset has been changed from calculating value * scale - offset to value * scale + offset. The offset for Sentinel-2 scenes with PDGS baseline >= 4.00 has been changed accordingly from 0.1 to -0.1. Now, the scaling behaviour in EOdal is the same as in QGIS.

In addition, there was a small bug in the mapper when calling it for Landsat with different sensor generations (OLI versus ETM). Bands that do not exist in the reference scene (e.g., bands OLI has but not ETM) are discarded to make sure all scenes in the collection share the same bands. The bands affected are mainly same auxiliary quality bands such as qa_aerosol. If you need to have, you have to make sure that you only select scenes from Landsat-8 or -9.

[codecov]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (0a5d341) 57.85% compared to head (49f3621) 57.78%.

❗ Current head 49f3621 differs from pull request most recent head 805fe24. Consider uploading reports for the commit 805fe24 to get more accurate results

Files	Patch %	Lines
eodal/mapper/mapper.py	27.27%	7 Missing and 1 partial ⚠️
eodal/core/band.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #94      +/-   ##
==========================================
- Coverage   57.85%   57.78%   -0.08%     
==========================================
  Files          68       68              
  Lines        5332     5342      +10     
  Branches     1071     1074       +3     
==========================================
+ Hits         3085     3087       +2     
- Misses       1937     1944       +7     
- Partials      310      311       +1     

Flag	Coverage Δ
unittests	57.78% <28.57%> (-0.08%)	⬇️

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