notes on updating to CIAO 4.16

We have just released CIAO 4.16 which comes with native macOS ARM support (which makes your mac laptops go brrrrr).

I note that for CIAO 4.15 we changed how the conda installation works (making use of conda-forge for various technical/legal issues) so the installation steps will likely need updating.

I would hope that the Sherpa code doesn't need much updating but if you do use group_counts (or any of the other group_xxx calls) then the behavior may change (it depends if you group then filter or filter then group, as the latter is where the behavior changes). There may be other changes, including from CIAO 4.15 (the notice/ignore/group/set_analysis/... calls now report the selected filter range for one).