Made some changes suggested by Michael Slattery to fix table level comments. Also...

Made some changes suggested by Michael Slattery to fix table level comments.  Also added in field level comments.

His remarks follow:

Table level comments weren't populating.  The empty tag is generated in XML, but not populated.  $table->comments() doesn't have a get_comments method, so that explains my if/else around $meth

Right now it produces 'comment' data elements with no attributes in the 'comments' tag.  If this is a bad idea please let me know.