add notebook layout
add Stack container
add StackSwitcher
add Revealer container
add Overlay container
add Scrollable trait + Layout container
add HeaderBar
add FlowBox + FlowBoxChild
add ActionBar
add ListBox + ListBoxRow
Merge pull request #20 from jeremyletang/layout-container

add layouts and containers
begin work on glibs list types
add List, more trait impls on List + SList
remove warning from test file
add notebook layout
add Stack container
add StackSwitcher
add Revealer container
add Overlay container
add Scrollable trait + Layout container