Packer only build process

Hi  !

This PR introduce a new build process based only on packer (the goal was to not download a big vagrant box nor a big Docker image).

First, it contains these PRs :
* SSL docker port support : https://github.com/mitchellh/boot2docker-vagrant-box/pull/71
* Packer 0.7.x compatibility(Parallels provider) : https://github.com/mitchellh/boot2docker-vagrant-box/pull/70
* Enabling default vagrant vboxsf share with docker 1.3.x : https://github.com/mitchellh/boot2docker-vagrant-box/pull/69

Secondly, it add these changes :
* Correcting the 42 layers AUFS bug, we can now use 127 layers in docker (See : https://github.com/boot2docker/boot2docker/issues/531#issuecomment-61740859 - in brief we create a partition and format it isntead of formatting the whole sda device)
* Moving to boot2docker 1.3.1 (instead of 1.3.0)
* Packer now use a shell script instead of inline script

It will use the original boot2docker iso file, and tune it using a provision script + boot2docker perisstence options added recently.
The boot2docker documentation says that if you have a userdata.tar in /<your device>/var/lib/boot2docker, then it will be unarchived in /home/docker/ at the end of the boot : it's seems to be a good idea to push the vagrant ssh keys here no ?