Update GCE source_image in the docs

builder/googlecompute: rename "Gsutil" to "Gcloud" now that we're updating "gcloud" and not "gsutil".

Also renamed files accordingly.

builder/googlecompute: added support for all standard VM images

[GCE] google compute builder is broken, gsutil update fails in newer images

Do not re-add floppy disk files to VMX

This commit fixes errors like this in the vsphere post-processor when using floppy files in the builder step:
Error: File (/var/folders/zl/57c1vmr532z_ryf1scw53_b9ycmxh7/T/packer964492999) could not be found

The configure VMX step re-adds the floppy files, so we need to configure the VMX and _then_ clean the VMX in that order.

Added support to use templates for more fields in null-builder and amazon-builder

builder/amazon: support for enhanced networking

website: Added documentation page for environmental variables. #1130

website: Fixed Rackspace example

builder/vmware/esxi: checksum iso upload to not always upload

builder/virtualbox: Accept VirtualBox release candidate version

packer: Fixed typo in error message

website: Specifically call out the comma after `"builders": [...]`

Install gox during build time

post-processor/vagrant: hyper-v

Just so that we can just run `make` without installing gox separatelyy