Add Stackup to list of CLI tools

[ps-jay]

Issue #, if available: N/A

Description of changes: Add Stackup to the list of CLI tools.

It's a nice tool that has two main verbs: up and down (there are others as well, it supports change-sets for example). These verbs are declarative and idempotent.

The down command succeeds if: the stack exists and successfully deletes, but also if the stack doesn't exist.

The up command succeeds if: the stack creates, or if the stack already exists and updates successfully, and also will cleanup/delete a 'create_failed' stack first.

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