Updated MeshConvert references to NekMesh

Updated MeshConvert references to NekMesh to be consistent with release 4.3.

Also added an ARCHIVE option to CMakeList.txt for the cylinder case since this seemed to be missing.

@ccantwel Whilst it was on my mind I put together this fix branch to update MeshConvert. I also do not think the link is working for the cylinder problem possibly because an archive was not being made automatically.

@ssherw Oops, I had not noticed the missing archive for the cylinder case. Thanks for fixing. I have updated the online versions too.

These changes look good, so will merge.

mentioned in commit dd304212

Status changed to merged