Add site.j2 file

[noelmcloughlin]

The Jinja in pillar.example should be moved to separare site.j2 file:

    {% set devstack_svc_name = 'KeyService' %}
    {% set devstack_enabled_services = 'mysql,key' %}
    {% set devstack_svc_version = 'v0.2.0' %}
    {% set devstack_svc_port = '50040' %}
    {% set devstack_password = 'devstack' %}
    {% set devstack_svc_type = devstack_svc_name %}
    {% set devstack_svc_endpoint = devstack_svc_name ~ devstack_svc_version %}
    {% set host_ip = grains.ipv4[-1] or '127.0.0.1' %}
    {% set host_ipv6 = grains.ipv6[-1] %}

Note: The site.j2 interface exists in http://github.com/saltstack-formulas/opensds-formula/ already.