[impala] Show table/column formats in the summary view

Beyond issuing a DESCRIBE statement, the column and table comments don't seem to be used or displayed anywhere else. It'd be REALLY nice when viewing the schema in Hue to be able to quickly see the comment description of the table or see the column descriptions. While you can view a table in the metastore it doesn't always show the column comments (see related issues) and it involves leaving the current page.