Lua cookie-changed API is broken for WebKit 2

[aidanholm]

WebKit 2 does not provide this signal, or expose the soup session at all, since it now resides in the Web process. As a consequence, filtering cookies is broken (all are accepted), and the cookie inspector no longer works.

Solutions:

1. Specify a persistent storage location, and hook onto the cookie changed signal. When it fires, read the cookie database, and compare with a cached copy to provide the same cookie-changed Lua API. Use webkit_dom_document_set_cookie() to modify cookies in the Web process as necessary. Very hacky.
2. Get a useful cookie API merged into WebKit. Preferable.