This commit moves the horizon code from contrib/horizon to
congress_dashboard to install as plugin. Added README for the same.
http://docs.openstack.org/developer/horizon/tutorials/plugin.html
Note: Passes basic testing with v2 authentication
This commit doesn't address issue with V3 authentication.It is being
fixed as part of Bug: #1602837
Implements: blueprint congress-horizon-plugin
Change-Id: I06da4a47f61739635e6f1756f773b236ebde55c9