Set up Gitlab issues, and try at best to populate old issues

Our Redmine server is dead with no hope of getting back Redmine data, so set up issues in Gitlab.

So:

• All issues that were in project "Redmine Placeholder" have been moved here; Redmine Placeholder has been deleted (this concerns tickets from #1498 (closed) onward and #1443 (closed) and #1444 (closed) which were reemitted there as they were under work at the time of the crash of the server).
• Placeholder issues were created to represent the 1495 issues that were on Redmine and are lost.
• The changelog was used to reconstruct what some of these tickets were about. This is a daunting task that has been done in an afternoon with a quick and dirty script; it is by no mean perfect but it is better than 1495 tickets with the exact same content. There is a bias here: the reconstructed tickets are those which were closed... The label "Redmine placeholder" has been removed from those tickets. When one line of text in the Changelog was associated to several tickets, the same content was put in each of them and the relation was acknowledged through the Linked issues feature of Gitlab. I have no way to sort out what were the specifics of each of these tickets.
• #1607 (closed) will deal with the restoration for tickets that were dealt with from March to the end of October of 2019, for which more informations are available.

At the time of this writing (before #1607 (closed) is done) 658 tickets remain with the Redmine placeholder label. It is important to underline that some of them were actually not related directly to the project: the same indexing was used for all the projects on this Redmine, and if MoReFEM was the most important one there were others (related to administration of M3DISIM computers, projects derived from Redmine, third party tools, etc...). From memory about 150 issues were present and not close, so around 500 of these tickets were probabbly not related to the project directly.