Dfsu read elements preserve order

[ecomodeller]

closes #689

• [x] 2d
• [x] 3d
• [x] Spectral

[ecomodeller]

After, consistency between values and coordinates.

[ecomodeller]

#632 is related closely to this PR

[ecomodeller]

@jsmariegaard Merging this PR broke some tests in modelskill related to skill 😐

FAILED tests/test_config.py::test_comparison_from_yml - assert 0.2330094096313094 == 0.2331039 ± 2.3e-07
FAILED tests/test_multivariable_compare.py::test_mv_skill - assert 0.2249234222997736 ± 2.2e-07 == 0.22792652
FAILED tests/test_multivariable_compare.py::test_mv_mm_skill - assert 1.3053589704786461 ± 1.3e-06 == 1.5610323
FAILED tests/test_multivariable_compare.py::test_mv_mm_mean_skill - assert 0.643293404624024 ± 6.4e-07 == 0.6246696
FAILED tests/test_pointcompare.py::test_score - assert 0.19863716489592623 == 0.19870695 ± 2.0e-07

But I suppose the expected scores are actually not correct, since the default algorithm is to use IDW interpolation and the nearest elements are out of order, but this needs to be verified.

[jsmariegaard]

Hmm, something for next week...