ls-remote: create '--sort' option

Create a '--sort' option for ls-remote, based on the one from
for-each-ref. This e.g. allows ref names to be sorted by version
semantics, so that v1.2 is sorted before v1.10.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>