Fix #15 - Revert "Disallow restarting locked tabs" partially

This reverts commit 133af49dd0cce7e74bdaf64210475f6c22c5060e.
Bug 755593 - Remove tabs-on-bottom mode
Bug 749804 - Remove add-on bar
Fix toolbar button icons
Merge branch 'cleanup' into nightly
Merge branch 'nightly' into develop
Tab Utilities 1.6pre12