Migrate from Parameter Store to a "real" data store

[chelma]

Description

As discussed in #43, Parameter store was a convenient way to store application state when bootstrapping the project but has substantial limitations. This task is to move to another, more scalable and full-featured data store for application state. The current front-runner is AWS DynamoDB, as it appears to have suitable features and reasonable pricing for our use-case.

Related tasks/considerations:

• We currently only store the config bundle metadata in S3 for most objects, resulting in many S3 API calls when listing the configs (see Add config-list command to the CLI #139)

Acceptance Criteria

• A written/reviewed migration plan that outlines how we'll map our current Parameter Store usage to the new data store
• Updated code/configuration to use the new data store