reading cookies/headers from context about thruster

[Tronikelis]

@trezm and I am confused about the headers and cookies, I have some suggestions:

I think clear differentiation between request and response variables is needed

So something like this:

// from
context.set("foo", "bar");
// to
context.set_header("foo", "bar");

// from
context.cookie("foo", "bar", &CookieOptions::default());
// to
context.set_cookie("foo", "bar", &CookieOptions::default());

// from
context.headers;
// to
context.res_headers;

// I am confused about the methods below,
// the `context.cookie()` sets the header and thats it
// so these methods won't return anything?

// from
context.get_cookies();
// to
context.get_res_cookies();

// not sure what this does
context.set_cookies(cookies);