FFE 13.10: curtin new development

[Description]
Curtin is the "fast path installer" being developed to run inside a rich environment and install a prepared image (cloud image or maas ephemeral image) to a disk, make necessary adjustments, and then reboot.

It has just landed in archive, but will need some improvements for usability and further integration with maas.

[Proposed Changes]
The new features that are still needed from curtin are:
 * support for copying from / inside overlayfs root
 * network setup improvements, allowing the user to specify network configuration.
 * finalization code for getting bootloaders installed onto disk so system reboots successfully.
 * general code clean ups and improvements
 * selection and installation of kernel if not present in image.

[Regression Potential]
There is very little expectation for regression at this point. curtin is a new
package and not used by many users.