Remove intersphinx from the docs build as it triggers network calls that
occasionally fail, and we don't really use intersphinx (links other
sphinx documents out on the internet)

This also removes the requirement for internet access during docs build.

This can cause docs jobs to fail if the project errors out on
warnings.

Change-Id: I71e941e2a639641a662a163c682eb86d51de42fb
Related-Bug: #1368910

None of our documentation references any external sphinx documents so we
don't need the intersphinx mappings.

This started as a rename from the old glance.openstack.org site to the
newer docs.openstack.org/developer/glance however they may as well be
removed if not used.

Closes-Bug: #1353817
Change-Id: I638c4eeab7d01ec2f26a0d9d532f0006f4f75e72

Similar to the other authentication methods that were documented,
like password and token, this patch will add a brief description
on how to authenticate with the oauth1 plugin.

Change-Id: I1b7cceb116d337be71576139601f34ca17563a50

Since oslosphinx is out, let's use it instead of hosting our own
themes and static files.

Change-Id: I5b507d35c90d0c0411d7751935b0e53328ca9311

Added a bit more information to the 'using-api-v3' section, about
using sessions instead of passing in arguments.
This overlaps with what is documented in 'using-sessions' but I
think it's still handy as most folks will likely go here first.

Change-Id: I352bda49e01362d3a5da9a79ceb34748552ef9ec

Explain the plugins that are provided and some information on how to
write new ones. This will obviously need to be expanded as more features
are added.

Change-Id: Ie67e93f2ed994c3702ac66e388cf216609dd44ff

Changes
* removed extraneous word from Introduction section

Closes-Bug: #1334915
Change-Id: I201ddb70a4d91e0d615e322abc43848993dee573