common: StepDownload can force an extension

Update AWS EBS builder to fix invalid params

Revert "Changing --region to --location"

This reverts commit f40fd36c.

According to the documentation below, `--region` is the current flag. If you're
using an older version of the tools that use `--location`, you can customize the
commands in your Packer config with `bundle_vol_command` and `bundle_upload_command`

- http://docs.aws.amazon.com/AWSEC2/latest/CommandLineReference/CLTRG-ami-upload-bundle.html
- https://www.packer.io/docs/builders/amazon-instance.html

Add 1/10th second delay between key events to VNC

virtualbox,vmware: http server should listen on IPv4

Updates to Into: Build An Image docs

website: Fix statement in machine-readable 'ui' type docs.

post-processor/atlas: fix index out of range panic

Tests were failing incorrectly when OpenStack environment variables were...

Fix digitalocean provider for private images [fixes mitchellh/packer#1792]

virtualbox/common: remove devices should delete floppy controller

builder/google: don't hardcode SSH timeout [GH-1781]

GH-1879

builder/aws: Add pre validate step, to validate things before building.

Fixes 'unknown configuration key' errors for 'only' and 'except'

check the region before do the ami copy to fix the duplicate ami [GH-2123]

"Name" parameter required for copying ami across regions [GH-2172]