We have a copy of the output from running just "terraform" in a page on
the website. It doesn't necessarily need to be kept 100% up to date, since
users can always run the command to get the result from the horses mouth,
but it's nice to keep it somewhat up-to-date to reduce use confusion.

Add `terraform debug json2dot` to convert debug log graphs to dot
format. This is not meant to be in place of more advanced debug
visualization, but may continue to be a useful way to work with the
debug output.

This commit adds the `state rm` command for removing an address from
state. It is the result of a rebase from pull-request #5953 which was
lost at some point during the Terraform 0.7 feature branch merges.

Fixes #7259.

Implemented internal plugin calls; which allows us to compile plugins into the main terraform binary

This introduces the terraform state list command to list the resources
within a state. This is the first of many state management commands to
come into 0.7.

This is the first command of many to come that is considered a
"plumbing" command within Terraform (see "plumbing vs porcelain":
http://git.661346.n2.nabble.com/what-are-plumbing-and-porcelain-td2190639.html).
As such, this PR also introduces a bunch of groundwork to support
plumbing commands.

The main changes:

- Main command output is changed to split "common" and "uncommon"
  commands.

- mitchellh/cli is updated to support nested subcommands, since
  terraform state list is a nested subcommand.

- terraform.StateFilter is introduced as a way in core to filter/search
  the state files. This is very basic currently but I expect to make it
  more advanced as time goes on.

- terraform state list command is introduced to list resources in a
  state. This can take a series of arguments to filter this down.

Known issues, or things that aren't done in this PR on purpose:

- Unit tests for terraform state list are on the way. Unit tests for the
  core changes are all there.

 - [x] Docs
 - [x] Command Unit Tests
 - [x] State Unit Tests

Closes #4820

This uses the `fmtcmd` package which has recently been merged into HCL. Per
the usage text, this rewrites Terraform config files to their canonical
formatting and style.

Some notes about the implementation for this initial commit:

- all of the fmtcmd options are exposed as CLI flags
- it operates on all files that have a `.tf` suffix
- it currently only operates on the working directory and doesn't accept a
  directory argument, but I'll extend this in subsequent commits
- output is proxied through `cli.UiWriter` so that we write in the same way
  as other commands and we can capture the output during tests
- the test uses a very simple fixture just to ensure that it is working
  correctly end-to-end; the fmtcmd package has more exhaustive tests
- we have to write the fixture to a file in a temporary directory because it
  will be modified and for this reason it was easier to define the fixture
  contents as a raw string