add render function to Template class

- have wfTemplate use render() from the template class

ultimately, for improved testing, would be nice to get away from
using wfTemplate entirely! this allows instantiating a template
and render it in the same way as wfTemplate.

Change-Id: Ie246ae35e70dbdee5147aa1ee1b9d7254690dcce
Merge "add render function to Template class"