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.