Dynamic UI should be split into parser and renderer

Currently we have only one input format for dynamic UI - UI specs, but with the support of Heat templates as main application definition it would be convenient to automatically derive dynamic UI layout from Heat template (given it is simple enough). So, it is desired to split dynamic UI into parser (3 different flavors: current dynamic UI, the one deriving UI from Heat template and possible the third one deriving UI from MuranoPL classes) and into renderer. Only one renderer will be provided at this time - the current one dealing with Django forms/fields/widgets.