Propose additional IAM Role Actions

Depending on what settings you use for the amazon-chroot builder additional actions needs to be allowed in the IAM role for the aws instance.

This patch does not include an exhaustive list of all alternatives, but only the changes I needed to do to get stuff working for me.
builder/amazon/ebs: Add config for target AZ.

Fixes [GH-536]
builder/amazon/common: Add AvailZone to StepRunSourceInstance struct

[GH-536]
Fixes missing entropy in the uuid package.

math/crypto is seeded with 1 and thus will create predictable UUIDs. Because
amazon-instance and amazon-ebs in the same second when building both targets
the timestamp in front doesn't help either. See #552
Arguments Prefix (--) was missing for (data)portconfig
Simplifies the implementation of common/uuid
Merge pull request #557 from zimbatm/unique-uuids

Fixes missing entropy in the uuid package.
Update CHANGELOG
Merge branch 'master' of github.com:mitchellh/packer into fix#536

Conflicts:
	CHANGELOG.md
packer: don't panic if can't write to UI
Merge pull request #558 from fabiang/virtualbox-sata

builder/virtualbox: arguments Prefix (--) was missing for (sata)portconfig
Merge pull request #550 from mitchellh/fix#536

builder/amazon/ebs: Add config for target AZ.
builder/amazon: rename availzone to availability zone
builder/amazon/instance: support AZ here too
website: remove extra period.
spelling mistake in comments
Added missing close-curly-brace to default value of execute_command.
Merge pull request #564 from mmercer-appneta/master

Added missing close-curly-brace to default value of execute_command in Chef Solo docs
Merge pull request #572 from ktruong7/format-issues1

Spelling mistake in comments
s/extremely to/extremely easy to/