new window icons

I love your jQuery UI theme, but I wanted a complete set of window manipulation icons, so I added three more in addition to the close icon.  I'm a coder, not an artist, so the icons might need some work...

![menu icons](https://f.cloud.github.com/assets/1906437/1795572/566694da-6a20-11e3-979a-dc12a6c52959.png)