Update ARM-8 for dynamic environment support

Currently, static environments may be created by adding custom
`[whatever]` sections to `puppet.conf`, and in the absense of a matching
environment, the defaults will be used. The defaults can be "dynamic" by
the incorporation of `$environment` in the `manifest` and `modulepath`
parameters. This pattern is very widely used for dynamic environment
creation.

This addition updates the armature to indicate how `Environment`
resource defaults could be used to enable dynamic environment support,
and adds a parameter `dynamic_environments` that may be used to disable
this behaviour.
Merge pull request #52 from hlindberg/master

ARM-8 add discussion tags/anchors
ARM-8 Added discussion link and fixed two typos in arm-8 index.
Merge pull request #53 from jpartlow/arm-8-discussion-link

ARM-8 Added discussion link and fixed two typos in arm-8 index.
Merge pull request #50 from hunner/arm-8_dynamic_envs

Update ARM-8 for dynamic environment support
Update ARM-8 for `environmentdir` support

As previously discussed in #50, dynamic environments must be understood
from some context available to the puppet master without environments.

This draft removes the `dynamic_environments` parameter and adds a
description of how `environmentdir` may be incorporated to support
dynamic environments.
Merge pull request #55 from hunner/arm-8_environmentdir

Update ARM-8 for `environmentdir` support
ARM-8 W.I.P add tentative goals, var bindings, improve env handling

This commit includes:
* Tentative goals and non goals
* Start of motivation for some goals
* Improved way of handling environments and dynamic environments
* Binding of variables (required since they are delivered by an ENC)
* Typos, and other small adjustments

A second document examples.md is added with user stores (unfinished).