The S3 endpoint URLs don't always include the region name. See:

    http://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region

This mapping is already provided by `goamz` via `region.S3Endpoint`,
so let's use it.

provisioner/ansible: more configuration options

builder/qemu: binary name to be configured

builder/qemu: handle reboots in the shell provisioner

builder/vmware: get host IP by creating & inspecting connection, allows hypervisor...

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

esx5, Get host IP by creating & inspecting connection, allows hypervisor to reside in other networks

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