Finalize high precision Real - finished, really :) documentation + put minieigen sources into Yade

So I am very happy that high precision Real works. In this merge request I am finalizing all this work. The commits in this branch are the direct sum of !375 (merged) + !381 (merged) + !376 (merged) + !378 (merged) + !400 (merged) + !379 (merged) + !362 (merged) + !380 (merged) + !365 (merged) + !382 (merged) + !390 (merged) + !391 (merged) + !392 (merged) + !393 (merged) + !397 (merged) + !394 (merged) + !364 (merged) + !412 (merged) + !413 (merged) + !414 (merged) + !415 (merged). All of them work separately, to make sure that later git bisect will work. On top of them I have added 14 more commits with some finishing touches. When they are all merged together and this merge request is rebased on them only these couple commits will remain. And the high precision Real will work. In this branch I will be now pushing documentation to describe everything that I have done here :)

After the patches which I sent to the mailing list are integrated it will work with original debian bullseye image. These patches are also here (the Vector4r bugfix is not strictly necessary).

Note: for easier rebasing on previous merge requests I am keeping this branch on the tip by adding commits from other MRs here, they all will disappear after a rebase and only a couple commits will remain.

EDIT: I have split this into several smaller merge requests: !412 (merged) + !413 (merged) + !414 (merged) + !415 (merged), after a rebase only documentation will remain here.