Plan: Add Language Bar on Taskbar and delete kbswitch

Language Bar does:

1. Display the current keyboard layout indicator (like kbswitch does).
2. Switch the keyboard by mouse and "fakemenu" action (like kbswitch does).
3. Display the IME icon if necessary and provide the menu items and actions.
4. Keep its presence on Taskbar.

Language Bar doesn't become the active window by mouse click.
Fakemenu can realize the menu-like UI without window activation.