Update license to CERN-OHL-S

This is a long overdue and uncontroversial switch from CERN-OHL-1.2 to CERN-OHL-S. It is an update but not a change of the terms in principle.

All files that specified a license only stated "CERN Open Hardware License" so I haven't changed this.

I note that "actuator_tension_band" specified v1.2, this may need to be removed or updated - after checking with the contributor in question.

I've also updated some contact details and version numbers.

I think it would be appropriate to ask @julianstirling and @jaknapper to approve this as well as @williamwadsworth and myself, just so there's a record we have all agreed on it. This has been discussed at various points in the past but never actioned - it is now required to comply with the terms of gitlab's education programme.