create infrastructure to provide longer term maintenance for older releases
We should make it straightforward to backport important fixes to previously released versions of paraview and occasionally produce new patch releases. Institutional deployments of ParaView will benefit from this for example as they can quickly overcome whatever features they come across rather than having to wait for the next release, which may have its own problems.
At a minimum we need public release-X branches and tags as well as a way to build one-off binaries for all three platforms. Ideally though ParaView's code review and merge, tagging, documentation and binary release processes will be extended to make it routine. Binary releases will likely require maintaining Linux, Mac and Windows systems (VMs/Docker Images or whatnot) that are consistent with the original build environment.