* helm.el: Issue #387 helm-next/previous-line move to beg or end of source when on top or bottom.
(helm-move-to-line-cycle-in-source): new.
(helm-move--previous-multi-line-fn): new.
(helm-move--previous-line-fn): Do it.
(helm-move--next-multi-line-fn): new.
(helm-move--next-line-fn): Do it.
(helm-move--beginning-of-source,
helm-move--beginning-of-source): new.