Add cursor-key navigation to launcher

[Mirco Müller]

Add the ability to navigate the launcher with cursor-keys, select items and open quicklists.

As per decision in bug 728935

"The backlight-pulsing of launcher-icons is meant to be the focus-indication for the keyboard-navigation highlight... not only for launching apps. This is approved by sabdfl."

[Mirco Müller (macslow)]

Just for reference I'm adding the proposed key-mapping to use for the launcher-navigation:
 - shortcut key to jump to the launcher (ALT-F1 proposed)
 - shortcut key to bring up the quicklist of currently selected icon (SHIFT F10 or CursorRight proposed)
 - shortcut key to move selection up to the previous icon (CursorUp proposed)
 - shortcut key to move selection down to the next icon (CursorDown proposed)
 - shortcut key to close an opened quicklist (ESC or CursorLeft proposed)
 - shortcut key to activate/start selected icon (RETURN or SPACE proposed)

[Erlan Sergaziev (sergeant)]

Now that Super key calls the launcher it would be logical that it puts keyboard focus on the first icon.
After that, Up/Down/Home/End should move around and Enter to switch/launch.

[Florian Boucault (fboucault)]

Design bug: https://bugs.launchpad.net/ayatana-design/+bug/702490

[Mark Shuttleworth (sabdfl)]

I really quite like the idea of using navigation from the panel menu,
left to the Ubuntu button (which would show the launcher if it were
hidden), then DOWN into the launcher. So we don't need another key to
activate the launcher for keyboard nav, just get there directionally
from the panel.

Mark

[Florian Boucault (fboucault)]

New design: https://bugs.launchpad.net/ayatana-design/+bug/733154