builder/amzon: fix race condition after launching EC2 instance

common/config: config filter function [GH-521]

Fixes #521

It is possible for an instance to not immediately exist after it is
launched. Previously, InstanceStateRefreshFunc would crash if this race
condition were realized.

This change takes the exact same approach of the function above,
AMIStateRefreshFunc, treating 'InvalidInstanceID.NotFound' as if there
were an empty result.

builder/digitalocean: Scrub config before logging

common: An SSH timeout should be treated as an error

/cc @netshade

provisioner/chef-solo: chef environment support

website: Updated web site doc. for avail commands list

* Single quotes around chroot command cause it to fail.
* The chroot command also gets passed through the CommandWrapper template, so having sudo would clash with however the user wants to run it.
* Fix spelling mistake.

Added a test for the failure.

Most of the scanner code looks like it's a modified version of
bufio.ScanLines, so I changed it to use that but always add a line feed.

Packer was using the original file reader when uploading, instead of the UnixReader /cc @mitchellh

/cc @mwhooker - I changed the interface up a bit to return an error,
since things should return errors in Go (the ui.Error bit was kind of
ghetto because it had no way to bubble that error up except through the
UI).

Using this, I made it so that the communicator uses both a
CommandWrapper and ShellCommand with chroot so that the chroot commannd
is also wrapped (it wasn't before).

I think the functionality of all this is the same but I'd love if you
could look it over and make sure.

/cc @mwhooker

build/amazon/chroot: command_wrapper to support sudo-less