[Notification applet] Another camelCaseRefactoring regression.
[Message Tray] Check for pending notifications before acting. Plus some cleanup.
[Alt-Tab] Remove blinking for attention-seeking windows.
[Alt-Tab] Let window-handling keyboard shortcuts work also in non-persistent mode.

And let Ctrl+n toggle window-minimized (free up Ctrl+r for other purposes).
[Alt-Tab] In preview mode, show the application icon in the window's top-left corner.
[Alt-Tab] Unify key-pressed and key-released handling. Execute some actions on key-release instead of on key-press.

Actions that should not be repeated if a key is left pressed down
are best executed on key-release. Close-window is one example,
Zoom is another.