LP1816480 Angular grid ARIA improvements

LP1816480 Angular grid ARIA improvements

Various navigation and "role" improvements to the Angular grid:

* Apply "grid", "row", "columnheader", and "gridcell" role attributes.
* Page-Down goes to next page
* Page-Up goes to previous page
* Shift-UpArrow extends selection one row up (spanning pages).
* Shift-DownArrow extends selection one row down (spanning pages).
* Shift-Arrow controls support reverse navigation for back-tracking to
  de-select certain rows.
** E.g. shift-up 3 rows then shift-down 1 will leave 2 rows selected.
* Control-A now selects all rows in the page.
** For consistency with the select-all checkbox, only rows in the
   current page are selected.
** Note we could add an option to extend the selection to all rows,
   but it would require pre-fetching all of the data, simimar to
   how grid printing pre-fetches.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>