New stack for release of Gauss v49r23 for Sim09

This stack is for a new release for Sim09.

It needs !97 (merged) as LHCb is released with cmake but Gauss needs to be released with cmt. For this reason it may require core software experts' attention.
cc: @clemenci, @bcouturi.

Release checklist (to be filled by the shifter)

• release build validation (to be checked with the MR author)
• RPMs deployment
• CVMFS installation
• web pages update