Adopt glance.store library in Glance

This commits removes the old `store` package from glance and adopts the
usage of the new glance.store library. The library was designed to
preserve backwards compatibility as much as possible. In fact, most of
the changes in this patch are related to function args ordering and not
function renames or workflow changes.

Some changes that are worth mentioning:

1. Glance store doesn't rely on a global config object. All config
options must be explicitly registered.

2. All store operations now accepted an optional context. This is a
fallout from the context not being required in the `Store` constructor
anymore.

3. Store drivers are behind a private package called `_drivers` and
they're not suppose to be accessed directly. Instead, functions like
`get_store_from_scheme` should be used.

4. Stores are disabled by default

5. All the store specific options are under the `glance_store` group.

DocImpact:
The old store related configuration options have been moved under the
`glance_store` section. However, the old options will go through a
deprecation path. That is, they'll still be read from the `DEFAULT`
section to give deployers enough time to update their config files.

In k-2, the deprecated options will be completely obsolete.

Closes-bug: #1291848
Implements-blueprint: create-store-package

Change-Id: Iaacc70993ad5da292b93de42bbecda73d53b19fd
API support for random access to images

This patch adds support for random access to images to the API v2. It's
possible to partially access the image data by passing the offset where
the image should be fetched from and the size of the chunk expected.

Note that not all stores support random access to image data. In such
cases, the API will return an error mentioning the selected store
doesn't support such a feature.

DocImpact:
Content-Range header is now parsed to support random access to image
data.

Implements blueprint: restartable-image-download

Change-Id: Iade692a8197a9a1d9532711a5c572c505e5e7d20
Merge "Adopt glance.store library in Glance"
Merge "API support for random access to images"
Imported Translations from Transifex

Change-Id: Ib7dc9c505b027eb97afb0fbd966515f926f96a0e
Fix VMware Namespace capitalization & description

The namespace had incorrect capitalization. Also,
added additional text in description to make people
aware that the properties only apply to the VMware
compute driver.

Change-Id: Ic1c3c333a1c70782a0780ace0323b2f6728bdd09
Closes-bug: 1367548
Fix CommonImageProperties missing ":"

The namespace had inconsistent naming when compared to
other namespaces.

OS::Glance:CommonImageProperties
 should be
OS::Glance::CommonImageProperties

Change-Id: Iea9860be66eb06250f8a53b8c44ab787e9c8082a
Closes-Bug: 1367545
Merge "Fix VMware Namespace capitalization & description"