documentation is required for network templates

[Aleksey Kasatkin]

Feature 'network templates' needs to be documented.
Information on templates is present in:
spec: https://github.com/stackforge/fuel-specs/blob/master/specs/7.0/networking-templates.rst
and other working documents.

[Aleksey Kasatkin (alekseyk-ru)]

Partial fix was merged: https://review.openstack.org/#/c/214607/

1. One comment in https://review.openstack.org/#/c/214607/9/pages/operations/templates-networking-ops.rst remains unresolved (template example in docs).
2. AFAIC, we have about no links in docs to this section.
3. CLI docs should address these changes (or should have a link to added section about CLI support).

[Aleksey Kasatkin (alekseyk-ru)]

Most points are covered for now. New ticket is created for tracking of remaining items: https://bugs.launchpad.net/fuel/+bug/1529061