Widget to expose the metadata catalog from glance

In Juno, Glance is providing a metadata definitions catalog[1][2] where
users can register the available metadata definitions that can be used
on different types of resources (images, artifacts, volumes, flavors,
aggregates, etc). This includes both simple tags and key / value pairs
(properties, specs, etc).

This widget will get the metadata definitions from Glance
and will let the user add the metadata to the resource being edited.
It provides value validation as well as description information
about the metadata.

An implementation for Images is included in this patch. Additional
patches will be made for other resource types.

This patch also removes Edit Image Custom Properties screen as new
widget provides the same functionality. To avoid regressions owner
property is added to Image Detail screen.

********************** TESTING **************************
You can test this code with Glance patches by following
the instructions at the bottom of this etherpad:
Go to: https://etherpad.openstack.org/p/j3-glance-patches
*********************************************************

[1] Approved Glance Juno Spec:
https://github.com/openstack/glance-specs/blob/master/specs/juno/metadata-schema-catalog.rst

[2] Glance PTL Juno Feature Overview:
https://www.youtube.com/watch?v=3ptriiw1wK8&t=14m27s

Implements: blueprint tagging
DocImpact

Co-Authored-By: Santiago Baldassin <santiago.b.baldassin@intel.com>
Co-Authored-By: Pawel Skowron <pawel.skowron@intel.com>
Co-Authored-By: Travis Tripp <travis.tripp@hp.com>
Co-Authored-By: Szymon Wroblewski <szymon.wroblewski@intel.com>
Co-Authored-By: Michal Dulko <michal.dulko@intel.com>
Co-Authored-By: Bartosz Fic <bartosz.fic@intel.com>
Co-Authored-By: Pawel Koniszewski <pawel.koniszewski@intel.com>
Co-Authored-By: Heather Whisenhunt <heather.whisenhunt@hp.com>

Change-Id: I335d4708f5ce8afe58fb88dbe9efd79e2c04fc9e
Merge "Widget to expose the metadata catalog from glance"