SceneJS#loggingElementId for Logging to Page

Remove SceneJS.Logging and SceneJS.LoggingToPage classes from the API.

Instead, support optional logging to a page element through a new property on the SceneJS.Scene node:

var exampleScene = SceneJS.scene({

    loggingElementId: "theLoggingDiv"

    }, // ...
)

Logging is also echoed to the browser console in any case.