All examples must work

So far I did small or cosmetic fixes in 17 examples. Currently 21% of examples (46 out of 215) are broken. But now you can see file examples/list_of_examples.txt to check which of those are broken. Also let's see what happens if I submit two Merge Requests separated by few minutes only (the other MR is from "small-doc-fixes" branch). Will it crash the rebuild pipeline?

Also I merged yade-dev/master into all-examples-must-work before submitting this Merge Request. Is that good or bad? I am not sure, lets see what happens and then let's update the DOCs accordingly. Also in these DOCs we should mention what to do with those dropdown menus below: "Assignee" "Milestone" "Labels" "Remove source branch when merge request is accepted" and "Squash commits when merge request is accepted", I ignore them for now :)