Add rendering interface

This PR adds the rendering interface and several renderer classes to the View package using the code written for the Issue Tracker application.  I've credited @elkuku and @b2z as they did write the original classes (based on our git history) and I've done some work to clean up the classes based on feedback on [the mailing list](https://groups.google.com/d/topic/joomla-dev-framework/-3TU_ab5M3A/discussion).