TablePager: Redo arrow icons from scratch as CSS backgrounds

Redrawn the images with SVG versions.

Intentionally did not preserve the value of the 'alt' attribute of the old
images, it doesn't seem very useful to me. Instead, added 'title'
attributes on the sort links that describe their action. This should be
more useful than the old version for both visual and aural mediums.

Bug: 69277
Change-Id: Ibaec75e81d3eb8338d911ac84d91570047f475f5