Move all dat schema into a centralized location, and support switching schemas

[angelic-knight]

Enhancement:
We should modularize all the schema-specific stuff so that we can potentially run the same PyPoE on multiple versions, by specifying a certain schema to use.

[pm5k]

I’ll be looking at PyPoe in depth at some point this week, I will try to update this issue with a generic sketch of what this could look like. There’s definitely a lot of pros to doing this, and I think that a config-based mapping of versioned schemas could be a good way to do this. Question is - how coupled is this currently with the main codebase and how easy would the decoupling be.