Speed up Numbers

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It seems like numbers themselves are quite slow. This should be fixed.

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It seems like the problem lies in the instantiation of the Numbers in the ArgumentContainer and it lies in the implementation of ICUs library. Maybe there is a way to avoid that instantiation completely.

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But it seems like the numbers are getting cached. This is good and bad at the same time as it means that the developers of that library know that this is a problem and they have done a more-or-less hacky solution so that that problem does not really occur that often.
This is good as many numbers occur quite often, but sometimes new numbers will appear which means that the slowdown is there again.