Extract ComponentJSONRenderer into tapestry-offline

[uklance]

Fork tapestry-cometd on github to a project named tapestry-offline and remove any push-specific code.

The interface might look something like:

public interface OfflineComponentRenderer {
   JSONObject renderComponent(ComponentEventRequestParameters params);
   JSONObject renderComponent(ComponentEventRequestParameters params, HTTPSession session);
   void renderComponent(ComponentEventRequestParameters params, OutputStream out);
   void renderComponent(ComponentEventRequestParameters params, OutputStream out, HTTPSession session);
   void renderPage(PageRenderRequestParameters params, OutputStream out);
   void renderPage(PageRenderRequestParameters params, OutputStream out, HTTPSession session);
}

[uklance]

@see https://github.com/uklance/tapestry-offline