core/keybindings: Use C-S-<cursors> instead of S-<cursors> for windmove

The S-<cursors> bindings are used for selection, use C-S-<cursors> for
windmove purposes instead.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
core/packs/pack-git: Enable commit sign-offs for magit

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>