Tech Debt: Use modules, safety enums, docs updates

[dogversioning]

This PR makes the following changes:

• Converts project to python module and removes absolute imports (technical debt: AWS python 3.9 supports __init__ #74)
• Converts transaction/study periods keys to enums, updates references to same (Tech debt: Create enum for all transaction/meta dicts, and use it instead of base strings #102)
• Updates docs for integration tests to reflect newest library cli (Rewrite integration.md doc to describe new pip-install flow for Library #79)
• Moves example AWS events to explicit examples dir(Move /events someplace more discoverable #93)
• Removes non-aggregator specific DNS info from example template

[mikix]

Once we target py3.11, we can just use StrEnum and enum.auto() values to get the lowercase version of the key. And I believe to use the enum directly in place of strings (i.e. no .value needed)

:wistful stare into the distance:

[dogversioning]

ok that is supported and i've already got a ticket for it (#104), and that enough is a motivator to do that. Seperate PR, though