Addresses [Issue #761](http://code.google.com/p/phantomjs/issues/detail?id=761).
This is a squash of 5 commits.
1. Complete reimplementation of the CookieJar and the Cookie API - Part 1.
The save/load mechanism is inspired by the Qt Demo "browser".
More info: http://doc.qt.nokia.com/4.7-snapshot/demos-browser.html
2. Making the CookieJar a singleton.
We need to have multiple NetworkAccessManager to monitor the network activity of the page,
but we also need to maintain 1 CookieJar: in this way we now have a shared bucket of Cookies.
3. Exposing the new Cookies API to the JS space.
* Updated the completions.
* Ensured backward compatibility of the API.
* It's now possible to "phantom.cookieEnabled = false" to disable cookies completely.
* New methods: addCookie, deleteCookie, clearCookies
4. Provided some internal Doc for the new Cookies API
5. Ensuring the "page.deleteCookie(name)" method works only if a cookie name is given.
We use the Qt Meta Object system to create an easily accessible QVariantMap
representation of the Key enumerator, such that we can now write something
like for example
page.sendEvent(keypress, phantom.keys.Backspace);
http://code.google.com/p/phantomjs/issues/detail?id=492