Fix comments about System Functions

This commit fixes comments about "System Functions".
 * Add a missing comment about System Functions in the header
 * Fix singular to plural like others

Change-Id: I3feb94cd11a6683ca80093574d60fdf7420e3af2
Make admin_bind_host configurable

The use case is running devstack inside an OpenStack vm and running tempest
from some other machine. To make the catalog export urls that can be accessed
from off the devstack machine, you need to set KEYSTONE_SERVICE_HOST to an
external IP. But devstack uses that address in its setup of keystone in
addition to exporting in the catalog. Because OpenStack has an issue where
a vm cannot access itself through its own floating ip, devstack fails. There
is no way to have this use case by providing an ip address. The workaround
is to use the hostname of the devstack machine. That worked until recently
when a change was made to set admin_bind_host to the value of
KEYSTONE_SERVICE_HOST. The result is that port 35357 is only opened locally.
This change allows the devstack user to restore the original behavior
allowing this use case.

Change-Id: I97b938b305b7dd878397e7e64462650064e59cd2
Closes-Bug: #1283803
Savanna: use heat infra engine if available

In Savanna we have two provisioning engines:

* "savanna" that directly work with nova/neutron/glance/cinder/etc and
   we'd like to deprecate it early in Juno release cycle, but it's still
   useful due to the fact that it could work ok w/o Heat;
* "heat" engine uses Heat for provisioning of cluster resources, it's
   currently under active development and we're ready to make it default
   for OpenStack installations with enabled Heat.

Change-Id: I937337b3921e9e51768a118fb4b6bd95962622bd
Merge "Fix comments about System Functions"
Merge "Savanna: use heat infra engine if available"
Merge "Make admin_bind_host configurable"
Merge branch 'master' of github.com:openstack-dev/devstack