Allow Qemu binary name to be configured

On some systems the default Qemu binary name of qemu-system-x86_64
isn't appropriate.  So expose the binary name as a configurable item,
allowing the user to set it to something more appropriate if they need
to.
enable qemu builder to handle reboots in the shell provisioner
Fixes #867: save private key when debugging gce builder

Signed-off-by: Prasanna Santhanam <tsp@qubole.com>
Formatted googlecompute builder as per `make format`
Add import_opts to the virtualbox-ovf builder. My use case is that I
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.
Use --url flag rather than --location for ec2-upload-bundle

AWS docs (http://goo.gl/rNZiCs) show that --location is deprecated and
to use the --url flag and reference the region endpoint instead.
Adding docs to #645 on the website

Setting `"ami_groups": ["all"]` will make the AMI publicly accessible.
Correcting website docs for this.
Merge pull request #894 from vogxn/docfix-ami-groups

Adding docs to #645 on the website
Add import_opts to the virtualbox-ovf builder. My use case is that I
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.
Merge branch 'bjj-add-importopts' of github.com:b2jrock/packer into bjj-add-importopts
esx5, Get host IP by creating & inspecting connection, allows hypervisor to reside in other networks
builder/vmware-iso: output upload error [GH-899]
website: update Vagrant PP docs for input artifacts [GH-898]
packer/rpc: fix crashes with big file uploads [GH-897]
communicator/ssh: set TCP keep-alive [GH-872]
communicator/ssh: fix build
Merge pull request #885 from rosstimson/ec2-upload-bundle

builder/amazon/instance: use --url flag rather than --location for ec2-upload-bundle
Merge pull request #883 from b2jrock/bjj-add-importopts

builder/virtualbox/ovf: Add import_opts to the virtualbox-ovf builder.
Update CHANGELOG
Merge pull request #870 from vogxn/master

builder/googlecompute: save private key when debugging gce builder