Region selector enabling multi-region support.

This patch adds a region selector dropdown
at the top of both the Project and Admin dashboards if
more than one region is available in the user's service
catalog.  The user is allowed to choose from any region
available in the service catalog. By selecting a region,
the user is limited to accessing endpoints in that
region only as long as the go through api.base.url_for

If there are more than one endpoint for a service in a
region the first in the catalog is returned.  Further
work on the blueprint will handle that complexity.

Supporting Keystone v2.0 and v3 catalog formats.

Partially implements blueprint multiple-service-endpoints

Change-Id: I1ab6539c7c5f4b1ae4b1716059370e86b6ca4d2e
Implement Browser session timeout

By default, Horizon just uses session, which expire, when the browser
is closed. This implements additionally a session timeout.

Change-Id: I140ee2ee37e092036a66d890d920423dfc493fba
Fixes: bug 1118441
Merge "Implement Browser session timeout"
Merge "Region selector enabling multi-region support."