LP#1825578: reverse direction of sort-order arrows in eg-grid

LP#1825578: reverse direction of sort-order arrows in eg-grid

This patch adjusts the arrow icons used to indicate if a column
in the Angular eg-grid is sorted to use the following convention:

  sort order ascending == display _up_ arrow
  sort order descending == display _descending_ arrow

To test
-------
[1] Apply the patch.
[2] In a grid with a sortable column (as can be found in /eg2/en-US/staff/sandbox),
    click on the heading to sort it. Verify that ascending sort displays
    the upwards arrow and descending sort the downwards.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>