Import manuals v4.2

This is an import and clean up of the NEMO manuals (~NEMO, TOP, SI³ ) in the last version of the code before the clean up of main.

I further cleaned up the repository and reduced the number of duplicated figure files (we should decide to use only one format!)

requested review from @acoward

assigned to @tlovato

removed review request for @acoward

requested review from @smasson

changed the description

This is an initial import, so I guess we should just merge it as changes are a lot ...

added 1 commit

• 460764cc - Update README.md

Compare with previous version

mentioned in commit 6ad69c36

merged