Only dump routes in the dumped file

[stof]

The context configuration should be kept separate from the routes. It should be configured from a separate place, allowing to dump routes independently of the context.
#111 changed the cache to cache routes only and generate the context on the fly, but this does not fix the case of dumping a static file.

In #111 (comment) I suggested to rely on reading the request context from meta tags by default (or from window.location for the very simple setup)

[stof]

Actually, the work was started in #130