Modify test_light_interception about walter HOT 5 CLOSED

It is my understanding that the test for shifts in light interception is only conducted for the main stem of the plant n°1. Is that correct @christian34 ?
If that is indeed the case, I think the test should be modified.
When the bug is present (i.e. when there are important changes in the intercepted PAR between one day and the next day), it does not affect all the plants and all tillers. If the test is only made on 1 axe of 1 plant, the bug can be present without being detected.

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I add test for all axes in #38

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The test is only conducted on a few days (which probably makes it a lot faster). Unfortunately it also means that the bug can be present without being detected. I think the test should be conducted on the whole simulation (nbj = 325 instead of 165).

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I think it would be good to refine the test to check for maximum variation instead of mean variation, because when the bug is present, important shifts only occur on a few days.

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done in #38

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