Settings: Keyboard Accessibility.

Make the activate/deactivate/configure links keyboard accessible.

The compiled CSS is coming in a subsequent commit.
Commit compiled css from previous change set.

Changed in e64ec4889455818fd7f76096d13d88b05581ac6e
Settings: Don't trigger search event on tab.

Keeps checkboxes checked when going back and forth with keys only.
Merge pull request #907 from Automattic/ticket/903

Better keyboard accessibility for modules listing page