Improvments for Router, Request and Response objects.

In the router, the first route matched handle the request.

Moved the send() code from a Response to the Router. This way, a body is
always completed when it matches a route.

Headers in a Request or Response getter to the Soup.MessageHeaders in the
respective message which provide much more flexibility.

Request objects have getter for their bodies and headers.
The path in a Request is a getter to the message uri path.
Isolated the server code from Router.

The router should not deal with the server responsibilities, especially
if we want to substitute the server in case of vsgi integration.

The code has been moved to the new listen api, which allow a server to
listen to multiple port.
Removed vars from request as it is not useful.

Variables to templates should be passed in the action, not through the
Response object.
Makefile uses a generic version of Vala.
Soup already display the libsoup and Valum versions.