builder/googlecompute: configure instance name

Retain the current default of an instance name generated by UUID, but allow
users to choose a specific one. Useful for provisioning with Puppet when a
node name is used to select the right manifest.

Ensure parent directories are created for base boxes, fixes #1059

Thanks, @mitchell!

builder/openstack: Add support for standard OpenStack environment variables

post-processor/vsphere: Add disk mode configuration to allow users to specify the desired diskMo...

builder/openstack: added support for gophercloud's PopulateApi

builder/amazon: configurable virtualization type

Fix ansible paths when provisioning Linux from Windows

implemented null buider

optionally use existing ssh key for amazon builders

Updates googlecompute build to v1 API & uses boot persistent disk

builder/vmware-vmx: add cloning support on Windows [GH-824]

Update Ansible provisioner to set cwd to staging directory.

Properly return error when invalid instance state is found

fixing colored output of Makefile