Data Collector mechanic and sample implementation

[adamsero]

This PR contains the last 3 commits from opl/timestamp_nodes_support_for_client

[sbernard31]

@adamsero, maybe I don't know what you try to achieve with your last commit but just in case :

In a general way, we don't use merge in Leshan, we prefer rebase to keep a clearer history.

In this particular case, IF you want to start your work based on #1255 and keep this PR THEN
I advice to rather reset hard your branch on data_collector branch
Then you can rebase it on master if you want (you can even squashed all commit from #1225 in one eventually)

[adamsero]

Sorry, that was unrelated, I accidentally updated a branch on our forked repo. I'm using a clean branch and I'll be adding the features gradually.

[sbernard31]

Ok no problem :)
(Eventually you can reset --hard your Przem83:opl/data_collector branch on commit 43ed69f, then push --force the Przem83:opl/data_collector branch, if you want to put this PR again in a "right" state)

[sbernard31]

Data Collector was replaced by Data Sender. (See #1274)