Try to integrate Freemarker decorating template compiler

[jvanzyl]

I've been using this implementation of Freemarker for a while (the initial impetus for making the template compilers pluggable) and I'd like to clean it up and make it available as an optional template compiler. I have tests in other project I need to migrate into:

https://github.com/jvanzyl/sitebricks-freemarker

Before calling it complete. It also has the concept of "bricks" but works differently than the standard Sitebricks way so I need to align that.