Add a reader for Meris L2 data

[johannesocean]

New reader for ENVISAT-MERIS data. The 4th generation reprocessing of MERIS data implements a Sentinel 3 like format including Level 2 products and TOA-radiances in the same dataset package. Hence, we can use the same reader as for the OLCI sensor. Basically we only add a yaml-file (meris_nc_sen3) and some minor changes to the OLCI-scripts

I will follow up with an extension of the TOA datasets in the upcoming weeks..

• [x] Tests added
• [ ] Fully documented

[codecov[bot]]

Codecov Report

Merging #1678 (4b520ee) into main (c34aebc) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1678      +/-   ##
==========================================
+ Coverage   94.30%   94.32%   +0.01%     
==========================================
  Files         306      308       +2     
  Lines       46043    46168     +125     
==========================================
+ Hits        43421    43546     +125     
  Misses       2622     2622              

Flag	Coverage Δ
behaviourtests	4.61% <0.00%> (-0.02%)	:arrow_down:
unittests	94.96% <100.00%> (+0.01%)	:arrow_up:

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

Impacted Files	Coverage Δ
satpy/readers/meris_nc_sen3.py	100.00% <100.00%> (ø)
satpy/readers/olci_nc.py	93.96% <100.00%> (+0.06%)	:arrow_up:
satpy/tests/reader_tests/test_meris_nc.py	100.00% <100.00%> (ø)

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[coveralls]

Coverage increased (+0.01%) to 94.908% when pulling 4b520ee060d8a68379f3ce9d4d6f85d43997f69c on johannesocean:feature-meris-l2 into c34aebcd0276e89f231a1cdb3f7a5fef3dfb4b55 on pytroll:main.

[mraspaud]

@JohannesSMHI Great start, nice that so much of the Olci reader can be reused! Now we are just waiting for the tests :)

[johannesocean]

@mraspaud Goodie! Should I create the tests as well, or will someone else do that?

[mraspaud]

I would say that you are probably the best person to do that :)

[johannesocean]

@mraspaud would you consider this PR to be "Fully documented" ?

[gerritholl]

@JohannesSMHI This sadly seems to have some merge conflicts by now. Any chance of looking into those?

[johannesocean]

@gerritholl, I´ll try to find time for this after my vaccation :)

[adybbroe]

@johannesocean @gerritholl and @mraspaud I just resolved some straight forward merge conflicts. Is this now getting ready to merge?

[johannesocean]

@mraspaud @adybbroe Glad to hear this has been merged! :)