in `ontoweave` allow different separators for different data files

I'm not aware if it's a bug or a feature, but at the moment the `-Ds` option appears to require to be put at the end of line, otherwise misinterpreting the rest of the line (such as other `table.csv:mapping.yaml` pairs) as its arguments, thus yielding error. This appears to prevent the user from using different separators for different data tables (when relying on `ontoweave` as it is). 
