Improve flexibility of olci level2 reader

[mraspaud]

This PR adds some flexibility to the olci l2 reader. In particular, it adds the the possibility to un-log10 the data which has units like lg(re mg.m-3) and lets the user provide its own mask items.

• Tests added
• Fully documented

[codecov]

Codecov Report

Merging #2504 (8d0ae24) into main (4642264) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2504   +/-   ##
=======================================
  Coverage   94.84%   94.85%           
=======================================
  Files         337      337           
  Lines       49571    49617   +46     
=======================================
+ Hits        47016    47062   +46     
  Misses       2555     2555           

Flag	Coverage Δ
behaviourtests	4.41% <0.00%> (-0.01%)	⬇️
unittests	95.47% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
satpy/readers/olci_nc.py	94.20% <100.00%> (+0.38%)	⬆️
satpy/tests/reader_tests/test_olci_nc.py	100.00% <100.00%> (ø)

[coveralls]

Pull Request Test Coverage Report for Build 5210366489

• 49 of 49 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 95.419%

---

Totals
Change from base Build 5208379223:	0.005%
Covered Lines:	47175
Relevant Lines:	49440

---

💛 - Coveralls

[djhoese]

This is also adds the ability to specify mask items right? Otherwise, looks good from what I understand.

[djhoese]

Doesn't this remove the calibration: "reflectance" from the DataID and .attrs?

[simonrp84]

Is that a problem if it does? It's not reflectance data.

[djhoese]

Not really, but I'm just pointing out that it did exist, now it doesn't. Since multiple calibrations don't exist I guess it doesn't matter.

[mraspaud]

yes it is removed, but it is A Good Thing (r) because it never was reflectance data.

[mraspaud]

This is also adds the ability to specify mask items right?

Yes, I mentioned it in the description of the PR :)