Added basic addon support.
The addon variables are now listed with the env list command
Merge develop
Added provisioning and deprovisioning of addons. Also cleaned up a few things in addon support.
Merge branch 'master' into feature/addons
Fixed the project choosing logic for add-ons.
Only print the add-ons header when add-ons exist.
Fixed the deprovision command's help text.
Preparing for release v0.6.0.
Corrected an issue when provisioning add-ons.

The output will not be correctly written without throwing an error.