Ctrl-Tab cleanup
Add Ctrl+Up/Down to navigate tabs in tab stack
Remember MRU tab order across sessions
Keyboard shortcuts cleanup
Add Ctrl+Alt+U shortcut key for Unstack Tab
collapseStack cleanup
Add Ctrl+Alt+[+/-] shortcut keys for Expand/Collapse Stack
Merge branch 'cleanup' into develop

Conflicts:
	defaults/preferences/prefs.js
Add Collapse/Expand All Stacks menuitem and shortcut key
Fix XUL overlay issue on Australis (#34)
Merge branch 'nightly' into develop
Tab Utilities 1.6pre18