01. Base template structure

The Symfony2 CMF does not provide base templates apart from the ones used in the symfony-cmf-standard and the demo sandbox. We put a base template into the project here.

Adding a base template structure based on YUI [pure css](http://purecss.io/) with the 'Landing Page' template.

Note that we still have defined no pages and no controller, so we can't see anything in the browser yet. (Except the lovely 404 page of Symfony2.)