Allow multiple root pages within aspect

[james-shaw-turner]

Currently inside an aspect you can only have a single "root page" that is loaded by the browser. Typically this is called index.html (or index.jsp on a servlet engine). This is the single page of a "single page app". There are use-cases when you want to launch a secondary browser window that is styled using some of the same resources as the main "root page" . To enable this we need to support multiple accessible HTML pages within an aspect. This will enable BRJS to support multi-page as well as single page apps.