Make nTomos warning an error

[bHimes]

Currently in "emClarity init" if the files int recon/ are present but either the appropriate .csv or .mod are missing from convmap, a warning is printed to the logfile.

This is intentional as a user may wish to ignore a file after template matching.

This also creates problems in automating larger projects, especially with mixed data sets.

Change this to an error, with instructions to move or remove the offending recon/files