Add new set of OpenStack modules

The new modules do all of the keystone v3 and are using common library
code to be consistent. These are aimed at consumers of the cloud -
subsequent os_ modules for cloud admin may have project names ... like
os_keystone_tenant, for example - with the reasoning being that an
end user of a cloud should not need to know service code names, but a
cloud administrator certainly knows what's running.
Except this one doesn't allow you to specify a floating IP that already exists, so maybe some convergence of the two modules is in order?