[ENH] Spectra: dask table support

[markotoplak]

All functionality should now also work for Dask tables, albeit perhaps slower.

In the future, individual curve display should work in the same way as average curves, which means it should be implemented in a thread.

[codecov[bot]]

Codecov Report

Merging #680 (5ba72dc) into master (6028631) will decrease coverage by 0.01%. The diff coverage is 84.21%.

:exclamation: Current head 5ba72dc differs from pull request most recent head 70142a8. Consider uploading reports for the commit 70142a8 to get more accurate results

@@            Coverage Diff             @@
##           master     #680      +/-   ##
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- Coverage   89.36%   89.35%   -0.01%     
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  Files          72       72              
  Lines       12000    12018      +18     
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+ Hits        10724    10739      +15     
- Misses       1276     1279       +3