Adding the data_image_registry panel for Sahara

The data_image_registry panel allows for tagging
images with the flavors and versions of hadoop that they
support.  Those tags are used in creating clusters to
be sure that a cluster has all the necessary pieces to
function properly.
This code was originally from:
https://github.com/openstack/sahara-dashboard

Change-Id: I647c03a0ce9b802dd1100bce49dc46e24cac7190
Partial-Implements: blueprint merge-sahara-dashboard
Co-Authored-By: Nikita Konovalov <nkonovalov@mirantis.com>
Co-Authored-By: Dmitry Mescheryakov <dmescheryakov@mirantis.com>
Rename Trove panels to remove redundant information

Currently all Trove panels in the navigation panel
are prepended with the word 'Database' - this is
redundant and wasteful of space as we get more /
longer panel names

Remove the word 'Database' from panel names in
the navigation panel

Change-Id: I481178c0aa1d99b2c775750a1f66fd2aa51e8647
Closes-Bug: #1336490
Consistent handling of choiceField for backups

CHanged the way we initially populate the restore
backups choice field in the trove launch dialog
so that it is consistent with other choice fields
in horizon dashboard e.g. compute->instances

An empty choiceField now says
'No backups available'
and a populated choiceFIeld will have an initial
selection of
'Select backup'

Change-Id: I1b0f57656bd649ad92268789f35c9ba77223dbc9
Closes-bug: #1340867
Display volume size for trove instances

Add volume size (in GB) to the trove databases
table and the database details page

Change-Id: Ia37e99c78cdb95a61772f2fa42c1b7f59a86aad8
Closes-bug: #1340900
Merge "Consistent handling of choiceField for backups"
Merge "Rename Trove panels to remove redundant information"
Merge "Display volume size for trove instances"
Merge "Adding the data_image_registry panel for Sahara"