Assert if {{render}} is called with an unquoted name.

Eventually, `{{render}}` should be similar to `{{partial}}` where an
unquoted templateName is used to do bound parameter lookup.

This PR updates the tests to use quotes, and adds an assertion if an
unquoted param was provided.
Merge pull request #3944 from rjackson/cleanup_unquoted_render_usage

Assert if {{render}} is called with an unquoted name.