Make it possible for layouts to override the html head entry set displayer.
Update copyright.
Merge pull request #92 from gauthierm/head-entry-set-displayer

Make it possible for layouts to override the html head entry set displayer
Add base dialog class that can be used to implement responsive JS dialogs.
Fix typo.
Remoev unused showBodyChildren() function and update updateLayout() function name.
Switch full_screen config to resize_mode and add a centering mode.
Only udpate positioning if the dialog is open in resize handler.
Move dialog header into scrollable element for dialogs.

This works much better for mobile.
Fix overzealous scroll-top behaviour.
Fix bad comment.
Add todo comments for animations.