Cookies 1.0 api (#217)

The main changes are:

* Use the Cookie and Set-Cookie headers as the sole source-of-truth instead of trying to keep a separate collection of cookies in the message object.
* Introduce a clear distinction between request cookies (key-value pairs set in Cookie header) and response cookies (individual Set-Cookie headers that have attributes like Domain and Path).

components/api/src/main/java/com/hotels/styx/api/FullHttpMessage.java

@@ -23,7 +23,6 @@
 
 import static com.hotels.styx.api.HttpHeaderNames.CONTENT_LENGTH;
 import static com.hotels.styx.api.HttpHeaderNames.CONTENT_TYPE;
-import static com.hotels.styx.api.support.CookiesSupport.findCookie;
 
 /**
  * All behaviour common to both full requests and full responses.
@@ -43,13 +42,6 @@ public interface FullHttpMessage {
      */
     HttpHeaders headers();
 
-    /**
-     * Return all cookies in this response.
-     *
-     * @return all cookies.
-     */
-    List<HttpCookie> cookies();
-
     /**
      * Returns the body of this message in its unencoded form.
      *
@@ -89,16 +81,6 @@ default List<String> headers(CharSequence name) {
         return headers().getAll(name);
     }
 
-    /**
-     * Return the single cookie with the specified {@code name}.
-     *
-     * @param name cookie name
-     * @return the cookie if present
-     */
-    default Optional<HttpCookie> cookie(String name) {
-        return findCookie(cookies(), name);
-    }
-
     /**
      * Return the {@code 'Content-Length'} header value.
      *