build bcpc-bootstrap via Packer

This change is to provide the means to build the initial bcpc-bootstrap
machine image having similar configuration to that of a bare metal
deployment.  The goal is have a functional machine image that mimics
that exact same state after PXE booting a bare metal bcpc-bootstrap node
and undergoing the typical installation procedure.
use bash for VBOX_DIR and P variables

* remove dependency on python
* ensure PWD is the same directory as the script
utilize Packer built images for bcpc-bootstrap

* provide helper functions for clarity
* use Packer if image does not exist
* import available image into VirtualBox
* automatically start the bcpc-bootstrap VM
remove manual download of Vagrant image

the usage of this image is now obsolete in favor of Packer + VirtualBox
insecure SSH key for bcpc-bootstrap image
simplify vbox_create.sh

* Utilize Packer for bcpc-bootstrap node
* Simplify creation of worker VMs
* Decouple bootstrap_chef.sh and enroll_cobber.sh from Vagrant
* remove Vagrant as a means of setting up local development install.
  Packer-based builds provide the image once built