Add a validation step to parameters schema

This enables validation of of the parameters section of the template, so
that operations like template-validate now return a proper error if
something is wrong.

Closes-Bug: #1265862
Co-Authored-By: cedric.soulas@cloudwatt.com
Change-Id: Ic5d67f18d7bc53fd3e4e765ca221e21be0b9546d
Add config options to specify stack domain admin

Adds config options to specify a username and password who can
administer the projects & users in the stack domain.  Note this
user must be a domain admin (have admin role in the domain)

Note this requires the following devstack patch:

https://review.openstack.org/#/c/76036/

Or for non-devstack deployments, the domain should be created via
python-openstackclient and heat.conf updated with the username and
password:

openstack --os-token <atoken> --os-url=http://<KS_IP>:5000/v3 \
    --os-identity-api-version=3 user create heat_domain_admin \
    --password <password> --domain <stack_user_domain id>

openstack --os-token <atoken> --os-url=http://<KS_IP>:5000/v3 \
    --os-identity-api-version=3 role add --user heat_domain_admin \
    --password <password> --domain <stack_user_domain id> \
    --domain <stack_user_domain id> admin

blueprint: instance-users
Change-Id: I8c5242d336e3fabafcd1930271408670af09fa0e
Merge "Add config options to specify stack domain admin"
Merge "Add a validation step to parameters schema"