Add light shadow under wp table column headers

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Revert "Workaround for cut-off horizontal scroll area"

This reverts commit 37db0c7674bb70568bacde47dca9d0a53fec4448.
Update table header widths on details pane toggle

Signed-off-by: Alex Coles <alex@alexbcoles.com>