Copy the preamble / summary of OAuth1 from the specs repo
Copy the preamble / summary of OAuth1 from the specs repo

the summary before the APIs in the current form does not render
correctly and seems incomplete in comparison, use the one from
the specs repo.

Change-Id: I2708cd63ab29bd8b65e7f13497e82444e4a2813a

openstack/keystone,ilay09/keystone,mahak/keystone,ilay09/keystone,cernops/keystone,rajalokan/keystone,ilay09/keystone,rajalokan/keystone,rajalokan/keystone,mahak/keystone,mahak/keystone,openstack/keystone,cernops/keystone,openstack/keystone