Freebsd 10 pkgng

This adds a template for the newly released 10.0 version of FreeBSD.

* Uses [mfsbsd](https://github.com/mmatuska/mfsbsd) to install the base image, reducing the size of the `install.sh` script compared to previous FreeBSD templates
* Uses binary packages as much as possible, in order to speed up the build

TODO

[ ] - Cleanup `<WAIT>` lines - find a prettier way to add them to the `boot_cmd_sequence`
[ ] - Create ZFS filesystems for `/usr/src` and `/usr/ports` so we can enable compression