Show attributes and values for SAMPLE columns

This adds an "uber column" of INFO, SAMPLE_1, ... SAMPLE_n
with respective attibutes/values uderneath them.

fixes #67
I don't think so—this object represents the columns to be displayed, including the major columns above the minor columns. I like that it's clear from the name that this object contains the columns to be displayed; all of the columns, not just the major or minor columns. Additionally, the structure of the object itself is documented clearly.