Add disk mode configuration to allow users to specify the desired diskMode to ovftool: eagerZeroedThick , seSparse, thin and think.  Defaults to thick per current ovftool default.
builder/virtualbox: Add an `export_opts` option

Allows arbitrary arguments to VBoxManage export, such as product info (--product, --vendor, etc).
Pass export_options individually to VBoxManage export
Move to an array of strings for a deterministic option separation
Log export command being executed
Properly apply templates to export opts
Fix export opts tests
Formatting
Fix ansible paths when provisioning Linux from Windows

Since the paths are generated on the host machine but the commands are
executed on the VM being provisioned the paths generated will use path
separators from the host. In the case of provisioning a Linux VM from
Windows this path will not work.

Convert the path to use a '/' separator which should work for both
platforms in Go
implemented null buider

The null builder is not really a bulider, it just setups a SSH
connection and runs the provisioners. It can be used to debug
provisioners without incurring high wait times. It does not create any
kind of image or artifact.
optionally use existing ssh key for amazon builders
fixing colored output of Makefile

The colored output is broken when using Zsh.

\033[32;01m==> Installing dependencies\033[0m
\033[32;01m==> Building\033[0m

After adding the parameter -e to echo I get the expected green lines.
Changing to the v1 google-api-go-client. Now creates a persistent disk as the boot disk, and sets it to auto delete
Add inventory_file option to Ansible provisioner.
builder/vmware-vmx: add cloning support on Windows [GH-824]
added %s for productVersion param
Update Ansible provisioner to set cwd to staging directory.
builder/amazon: configurable virtualization type
use old ssh code until higebu's branch is ready, see #1019
builder/digitalocean: updated default image_id, per #1032