Replace Havana references with Icehouse

Fix URLs to point to Icehouse, now docs.openstack.org/icehouse
is available.

Change-Id: Id614a8c7b43d707436369675d946d2a70896dd23
Clarifies that continuously-published guides are "current"

- The icehouse nomenclature on each page was confusing to some

Change-Id: I6b76962c2e26fff8608a0c7c32a60effcdc98150
Merge "Clarifies that continuously-published guides are "current""
Merge "Replace Havana references with Icehouse"