build_image, image_to_vm: add disk-size assertions

Assert that the image is a multiple of 1 MiB
azure: finalize azure image

Increase the root partition to ~28 GiB.
Merge pull request #337 from crawford/azure

azure: finalize azure image
ami: wait for new volume to become available before attaching

Today EC2's volume creation is a bit less instant than usual.
Merge pull request #340 from marineam/ami

ami: wait for new volume to become available before attaching
offline_signing: download from stable, it gets built/uploaded first.
Merge pull request #341 from marineam/download

offline_signing: download from stable, it gets built/uploaded first.
grub_install: use sudo when reprobing
build_library: use jq to parse JSON
Merge pull request #342 from crawford/sdk_fixes

Various SDK fixes
add pcie configuration to vmware vmx file
use pvscsi device
use vmxnet3 device
ami: add eu-central-1 to list of AWS regions
Merge pull request #344 from crawford/ami

ami: add eu-central-1 to list of AWS regions
scripts/oem/ami: consolidate regions and AKI ids
scripts/oem/ami: bump PV-GRUB AKIs to 1.04 in all regions
Merge pull request #345 from crawford/ami

Clean up AKI lists and bump to 1.04
vm_image_util: generate qcow2 images compatible with QEMU < 1.1
disk_util: ensure partitions are layed out on disk in order

So far the default iteration order of python dicts has mostly matched
the order that we want the partitions on disk but this is not always the
case. I caught the BIOS-BOOT partition being ordered on disk after the
USR-A partition. Nothing bad came of this but consistancy is good.