Initial commit for feedback to support sdl dub packages

Don't look into merging this pull yet, I just wanted to get some feedback (I haven't implemented SDL parsing yet). Since the Json type litters the code everywhere I though I would continue using it for now.  So the parseSdl function will actually return the Json struct.  I plan change the name of the Json struct to something else but it will otherwise look very similar.  I think this is the easiest way to support multiple formats, what do people think?