users/algernon[@bombadil]: Use smart-mode-line

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
packs/pack-smart-mode-line: Move SML configuration to core

Install smart-mode-line from the core, and move configuration there from
the user config. It may be useful elsewhere too.

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