Update Kibana documentation
Update Kibana documentation

Simplify some of the Kibana docs, and add some more detailed information
on searching logs.

* Add a summary of what Kibana is

* Make it easier to see how to access Kibana (e.g. say port 5601 instead
  of <kibana_server_port>)

* Add note how to enable Kibana via centralised logging

* Expand the search section with an example.

Change-Id: Ia01e2b52fa758eb45fa417da7c6622150b2d5156

nihilifer/kolla,GalenMa/kolla,intel-onp/kolla,stackforge/kolla,nihilifer/kolla,stackforge/kolla,rahulunair/kolla,coolsvap/kolla,GalenMa/kolla,coolsvap/kolla,stackforge/kolla,coolsvap/kolla,mrangana/kolla,rahulunair/kolla,openstack/kolla,intel-onp/kolla,mrangana/kolla,openstack/kolla