Add extension discovery to core API.

Add a mechanism to discover the extensions that are available on the
server and the entry point to using them.

Change-Id: I40d90085aa546e4eb78acd86e9e67b4c8d27c875
Google Analytics code needs to be UA-17511903-1

Seems like https://review.openstack.org/#/c/37264/
did not stick

fix bug 1196922

Change-Id: I6072e3f05da59b9dcc0437717d901f08eb39ca48
Merge "Google Analytics code needs to be UA-17511903-1"
Merge "Add extension discovery to core API."
fix links internal to oauth spec

Change-Id: If114bce10ebe635af8065f1f1f79c105a09bf620
rename request_token_key -> request_token_id

this is how it's referred to in the implementation, and is
self-consistent with the other key/id references in the document

Change-Id: I48bb14167fa7b7dd5f550ef4b82b8df2a0276988
Add consumer id to token returned from OAuth

Add a consumer id field to the token that was returned from an
oauth signed call to /auth/tokens

Change-Id: I245a4301d7022ad85dbdf958cbc10ecc4921b1ea
Merge "fix links internal to oauth spec"
V3 schemas

Change-Id: Ie3aecbf494df37a7b0dae18d8fbb0659fd9719df
Merge "Add consumer id to token returned from OAuth"
Add an example request that shows oauth1 method

In the section labelled `Request an Identity API Token`, we need to
add an example of a auth body that shows oauth1 as an authentication
method.

Change-Id: I260d38dc922ba52b9441fdf4a7ced821ff2910ec
Merge "Add an example request that shows oauth1 method"