builder/googlecompute: save private key when debugging gce builder

builder/virtualbox/ovf: Add import_opts to the virtualbox-ovf builder. 

builder/amazon/instance: use --url flag rather than --location for ec2-upload-bundle

have existing virtualbox virtual machines where I need to keep the mac
addresses so that the network interfaces come up when packer boots them.
Otherwise I just get SSH timeout and I'm unable to configure the machines.

Adding docs to #645 on the website

Setting `"ami_groups": ["all"]` will make the AMI publicly accessible.
Correcting website docs for this.

AWS docs (http://goo.gl/rNZiCs) show that --location is deprecated and
to use the --url flag and reference the region endpoint instead.

have existing virtualbox virtual machines where I need to keep the mac
addresses so that the network interfaces come up when packer boots them.
Otherwise I just get SSH timeout and I'm unable to configure the machines.

Signed-off-by: Prasanna Santhanam <tsp@qubole.com>

Change the word `aws_access_key` to `aws_secret_key`.

website: update defaults for DO ID's

/cc @mmckeen

/cc @mmckeen - Did a refactor here, CC'd in case you're curious
or want to learn :)

common: set user agent in downloader

builder/virtualbox,vmware,qemu: add more special scancodes

provisioner/ansible: upload playbooks correctly

website: fix typo in qemu documentation