v1.6pre14

Changes since 1.6pre13:
Improved: Show locked indicator above tab favicon
Improved: Raise discoverability for multiple tab handler
Improved: Rename "Select a Tab" to "Mark Tab"
Improved: Rename "Select Multiple Tabs (+)" to "Mark Multiple Tabs"
Added: "Mark Multiple Tabs" menuitem
Added: "Select Similar Tabs" menuitem
Removed: Customization for Protected/Locked tabs

Fixed: Fix icons for Pale Moon
Fixed: Fix Tab Groups button icon
Fixed: Fix Mac full screen exiting