support # CSV comments #649

Is it possible for SA to skip commented-out lines?
When working on complex data (eg right now an electrical Asset Management meta-model) I sometimes need to comment-out a line before I decide to keep it or delete it altogether.

• https://www.w3.org/ns/csvw has commentPrefix (part of csvw:Dialect)
• I've requested it in TARQL tarql should support comment-prefix (# by default) tarql/tarql#108
• https://sparql-anything.readthedocs.io/latest/formats/CSV/ doesn't mention "comment"
• the underlying library https://commons.apache.org/proper/commons-csv/apidocs/org/apache/commons/csv/CSVFormat.Builder.html#setCommentMarker(char) has commentMarker but it's unclear whether it's for writing (in particular a header comment before the header line), or also respected on reading

If this is a useful feature, then we can discuss:

• one char or regex?
  One char is more than enough IMHO
• for the whole row or cell by cell?
  Definitely whole row
• option name: could be csv.commentMarker

Thanks!