Merge branch 'alt-tabs' into ext4-theme

lib/jsduck/tree_icons.rb

template/app/History.js

template/app/LocalStore.js

template/app/controller/Classes.js

template/app/model/History.js

template/app/store/History.js

template/app/view/ClassGrid.js

template/app/view/Viewport.js

template/app/view/cls/Container.js

template/app/view/cls/Overview.js

template/app/view/cls/TabPanel.js

template/app/view/index/Container.js

template/app/view/tree/Tree.js

template/resources/images/drag-bar-center.png

template/resources/sass/viewport.scss