Make LoadEventNexus run LoadIDFFromNexus re #7154

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Tidy up logging re #7154

Still need to make child algorithm LoadIDFFromNexus quiet, if it does not find an IDF in the Nexus file.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>