core: Adding ldap server ordering algorithms factory

The following adds ldap server ordering logic as preparation
for using it instead of Ldap server scoring.
This is required in order to support hardcoded ldap server list
per domain, and let the ordering of server effect the scording

Bug-Url: https://bugzilla.redhat.com/894681
Change-Id: Ic0904f9f6d9431ecac1cebee2790eae902a1329c
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>