GUAC-326: Add event target. Add placeholder input method radio buttons. Add more menu styling.
GUAC-326: Add notification for mouse emulation type change. Use it to signal completed downloads while we're at it.
GUAC-326: Remove GuacUI component object. Make OSK global.
GUAC-326: Add support for text input. Fix bug in handling of Ctrl-Alt-Shift (keys need to be released).
GUAC-326: Fix handling of focus (do not try to enforce, but inform when focus is gained/lost).