status: remove global up/down keyboard shortcuts

The widget still honors up/down when the widget has focus so disable the
global shortcuts since it interferes with being able to jump between the
"summary" and "description" fields using the up/down arrow keys.

Signed-off-by: David Aguilar <davvid@gmail.com>
commitmsg: simplify the way we handle up/down arrow keys

Add QActions so that we can do without needing to trap the arrow keys in
a keyPressEvent().  This is much simpler.

Signed-off-by: David Aguilar <davvid@gmail.com>