[ipvs, cluster] new plugin for IP virtual server

Remove the ipvsadm command collection from the cluster plugin and
put it in it's own plugin. Also collect connection entries with
'ipvsadm -Lc'.

Fixes #302.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
[keepalived] new plugin

Fixes #302.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>