[ADD] Pseudo `clone` mode for <templates> using primary="True"

When @primary="True" is present on <template> tag, we'll set
the t-name to the full canonical xmlid of current template (@id)
Providing a "kind of" clone mode for templates.
Merge pull request #491 from odoo-dev/master-primary-templates-fme

[ADD] Pseudo `clone` mode for <templates> using primary="True"