v1.6pre16

Changes since 1.6pre15:
Added: Add "Duplicate Tab to New Window" menuitem
Added: Add "Duplicate Tab to New Group" menuitem
Added: Expose Tab Stacking options
Added: Expose Tab Pinning options
Added: Expose Tab Unloading options
Improved: Don't stack duplicate tabs
Improved: Pick stack color from favicon
Improved: Enhance "Load URL from Clipboard" to load multiple urls
Improved: Refine tab hovering/scrolling options UI
Fixed: Fix UndoCloseTab status on startup