Implementing a migration path to 3.0

This release ensures that the API Gateway custom resource that is used by CF will be able to migrate to the version that will be released alongside 3.0.

The main goal was to make sure that the CF resource that is currently used is correct and does not too eagerly delete stages and APIs. The next version will include a new resource that will likely start replacing the existing resources, and as such the two need to be able to not interfere with one another.

PLEASE RUN lambda setup BEFORE USING THIS VERSION