Merge release-6.6 into develop without the shark revert

This is the merge of release-6.6 into develop plus a revert of the revert of the shark upgrade. As discussed in !117 (merged). What I did:

git checkout develop
git checkout -b merge-6.6
git merge release-6.6
git revert 81bed5aee5facd4435b030d81993b660a8e38083 -m 1

I decided to do it in a feature branch against develop, instead of into release-6.6 directly (as suggested by @gpasero in !117 (merged)), so that in case we make a minor release 6.6.1, we can decide if it will contain the upgraded shark dependency independently of develop (which does).

Question: This also contains the fixes related to OpenMP activation for Debian (that enables openMP if shark is built with openMP, etc.). This is something we want in develop, correct?