website: includes information about "provider"

none

website: really fix puppet provisioner cmd docs

builder/docker: include user vars for docker configuration

Implemented initial working version
of Docker image importing code. #774

Login to a docker index now works, ready for
implementation of the actual push logic.

Implement login to a docker registry, error handling

mitchellh/packer's docker branch. #774

builder/virtualbox-ovf: fix shutdown_timeout handling

The shutdown_timeout config parameter was being ignored
(for both the user setting and the "5m" default) on the
virtualbox-ovf builder. As a result, packer complained
of timeouts on graceful shutdowns, and the build process
would error out. This fixes that along with some newly
created tests.

website: correct default puppet provisioner command

Documentation/docker: link pointing to dockerfiles was incorrect