Add machine_type option for qemu builder.

On CentOS7, ``pc-1.0'' qemu-kvm machine type are not supported.

Supported machines are:
none                 empty machine
pc                   RHEL 7.0.0 PC (i440FX + PIIX, 1996) (alias of pc-i440fx-rhel7.0.0)
pc-i440fx-rhel7.0.0  RHEL 7.0.0 PC (i440FX + PIIX, 1996) (default)
rhel6.5.0            RHEL 6.5.0 PC
rhel6.4.0            RHEL 6.4.0 PC
rhel6.3.0            RHEL 6.3.0 PC
rhel6.2.0            RHEL 6.2.0 PC
rhel6.1.0            RHEL 6.1.0 PC
rhel6.0.0            RHEL 6.0.0 PC
q35                  RHEL-7.0.0 PC (Q35 + ICH9, 2009) (alias of pc-q35-rhel7.0.0)
pc-q35-rhel7.0.0     RHEL-7.0.0 PC (Q35 + ICH9, 2009)
openstack builder error out when gets blank keypair
OpenStack builder: Make region not required

Perhaps "region" is required when using a public provider like
Rackspace? It's not required for my private cloud from Metacloud. I
suspect a lot of private clouds have only a single region and thus don't
need "region" to be specified.
Make region required for rackspace but not other providers

Update test to make it pass.
Use Region not S3Endpoint
Updating check for version when on devel.
Updating Ubuntu 12.04 ISO location and checksum
Add table of contents link to orphan doc: `other/environmental-variables.html`.
Add `page_title` attribute to each documentation file for which it didn't already exist, matching the value to each page's h1, respectively.
Merge pull request #1440 from legal90/master

Enhancements for Parallels builder
builder/parallels: Added some navigation keys. Fixes [GH-1442]
Merge pull request #1443 from rickard-von-essen/prl_nav_keys

builder/parallels: Added some navigation keys in "boot_command". Fixes [GH-1442]
Update CHANGELOG.md
add ability to set api url in template

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
fix missing parts

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
It's not necessary to use an instance-store image to build an instance-store image, see this example http://sorcery.smugmug.com/2014/01/29/instance-store-hvm-amis-for-amazon-ec2/ so there should be no restriction on the ExpectedRootDevice
Merge pull request #1453 from manul/master

builder/amazon-instance: It's possible to create instance-store images from EBS-based images
Update CHANGELOG
Merge pull request #1448 from vtolstov/simple

builder/digitalocean: add ability to set api url in template
Update CHANGELOG