Improved accessibility for tab key navigation in tables

When using the tab key to navigate to the first cell in a table, the cell itself was taking focus instead of the link and the link did not open when 'enter' was hit. Instead, hitting tab a second time opened the link. By default, the standard was to have tabIndex set on the first cell of every row for accessibility so the link inside the cell gets the next level of focus. To resolve the navigation issue and avoid user confusion, while adding `tabIndex` to first cell of every row, the system will check for focusable content and avoid adding `tabIndex` to `td`.