Metadata Definitions Catalog

A common API hosted by the Glance service for vendors, admins,
services, and users to meaningfully define available key / value
pair and tag metadata. The intent is to enable better metadata
collaboration across artifacts,services, and projects for
OpenStack users.

This is about the definition of the available metadata that can
be used on different types of resources (images, artifacts,
volumes, flavors, aggregates, etc). A definition includes the
properties type, its key, it's description, and it's constraints.
This catalog will not store the values for specific instance
properties.

Co-Authored-By: Travis Tripp <travis.tripp@hp.com>
Co-Authored-By: Lakshmi N Sampath <lakshmi.sampath@hp.com>
Co-Authored-By: murali sundar <murali.sundar@intel.com>
Co-Authored-By: Wayne Okuma <wayne.okuma@hp.com>

Change-Id: I03219cf5168d9c22d07aa38653f8a9fb7ea380b8
Merge "Metadata Definitions Catalog"