A bunch of fixes to express declaration

Disclaimer: I'm new to TypeScript, Node.js and express.js. I wanted to be able to import express and have it usable in a way that is close to the JavaScript usage. At first I had troubles getting importing to work, the Response class did not support calling end etc. I started reading the specification and found some threads about how to write declaration files and this is what I came up with. Sorry for putting it all in one commit, would have been too annoying to split it up after I moved most interfaces into the e module.

The end result is that you can import express, call it as a function and access members from it. Additionally it doesn't pollute the global namespace with members that have Express as a prefix.