Improvements to autobooking examples from mkanalysis, and to path-finding failure messages

Improvements to the path-finding failure messages, swapping the ref data search logic to prioritise .yoda.gz (as .yoda will fail for all std analyses now). Mkanalysis now reduces duplication and deactivates autobooking code if no HEPData ref data could be downloaded, as an upgrade from behaviour triggered only on MC_-prefixed analysis name. Code cosmetics and a little ONNXrt message finesse, too.