Add ability for Header widget to have child widgets

[#82420068] @evanweaver
Connect up the column header widgets

[#82420068]
Move example "lights only filter" into column header

[#82420068]
Select/Clear all checkbox working

 * Still to do: the checkboxes don't update properly

[#82420068]
VERY heavy handed way to make sure checks update

@evanweaver you might want to refine this

[#82420068]