Changes for 10.9 support

- Detect a 10.9 ESD and make the new ISO out of BaseSystem.dmg by converting to RW, growing it and installing Extras there
  - It's very possible there is a more efficient method to do this
- Xcode CLI tools script uses install-on-demand trigger file and a bunch of shell pipes to install from SUS
Add 10.9 BOM list for building on 10.7. Thanks to Rich Trouton for finding and adding this.
Support for building 10.9.