Enable searchlight integration for the instances table

Summary:
Provide Searchlight Integration for the Instances Table

Motivation:
Enabled taking advantage of magic search and searchlight (https://wiki.openstack.org/wiki/Searchlight)

Searchlight provides dramatically improved searching capabilities and performance.

Description:

Searchlight provides an elastic search based indexing service for OpenStack resources, including instances. It is optionally deployed and is discoverable via the keystone service catalog (service type = search).

You basically follow the following algorithm:

1) Is the search service enabled for the current scoped region?
2) Is the requested resource type indexed (query to searchlight) e.g. is OS::Glance::Images enabled?
3) Use searchlight for listing / querying
4) Query for available facets / facet options (to load magic search)
5) Display results

We also probably will want to provide an override setting to enable / disable using searchlight even when it is available.

This was demo'd for instances at the Liberty summit.

UX:
The UX will look and work similarly.

See: https://youtu.be/eGnGr48E5_4

Outside Dependencies:
Searchlight

Requirements Update Required:
None - There is no searchlight client. Direct queries will be made.

Doc Impact:
There will need to be documentation on enabling searchlight integration.