Accessibility Enhancements: Style properties for focus-states

While XenForo does a nice job on focus states, providing dedicated controls for them beyond search & basic inputs would be ideal. In some customization cases additional CSS must be added to ensure focus states for links and buttons are visible (such as monochromatic designs), and most users aren't aware of the importance of focus states. Providing a direct control for them via style properties would assist in that regard, allowing control of colors and borders (as well as an extra css/less...