Freebsd 10 Template

This adds a template for the newly released 10.0 version of FreeBSD.

### Features

* 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

### To Do

- [ ] - 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
- [x] - Clean up tmp 
- [ ] - Zero out extra space to help compress the image when exporting, similar to [vagrant-freebsd](https://github.com/wunki/vagrant-freebsd/blob/master/bin/vagrant-setup.sh#L87)
- [ ] - Remove packages that are `build-deps` for `virtualbox-ose-additions` port after build is complete?
- [ ] - Remove `/usr/src` and `/usr/lib32` and `/usr/ports` after `virtualbox-ose-additions` build is complete?