Add options to control column number printing

[spookylukey]

The current behaviour is to output a line for every AST match, which could be multiple per line, including column numbers. This is a good default, but we might want to add an argument to control this:

--column=none
--column=first
--column=all  # the current behaviour

--column=first would be the same as ripgrep's rg --column

I'm not sure how useful this would be in practice, so I'll only work on it if there is significant interest.