Made ordinary and fast ASCII readers store comments in Table .meta

This is meant to address #3136.
Why do you store the information in `meta['table']['comment_lines`]`? Would it not be easier to have that at the top level `meta['comment_lines']`? Since we are talking about a table object, I would expect all meta information to be related to the table anyway, so if I need to type `mytable.meta['table']['something']`that seems kind of a double effort.