Improve WidgetScrollBox
Cleanup headers and allow adding children to WidgetScrollBox
Fix memory leak
Add activate() to WidgetScrollBox

This allows us to activate child widgets inside of a WidgetScrollBox via
the keyboard.
Scroll WidgetScrollBox properly when selecting child widgets
Merge pull request #2 from dorkster/scrollbox

Fix child activation and scrolling for WidgetScrollBox
Simplify tab switching in GameStateConfig
Merge pull request #3 from dorkster/scrollbox

Simplify tab switching in GameStateConfig
Remove unneeded code
Merge pull request #607 from igorko/scrollbox

Improve keyboard navigation in Config Menu