Feature/multiple schemas

[lvlvllvlvllvlvl]

Abstract

Support switching specifications as per #21, and restore spec generation from the json schema

Action Taken

• Removed the _default_spec global variable and add a specification parameter to RelationalReader (defaulting to the current default, stable.specification) and DatReader.
• Import specification from schema json
  • Added a new specification file, generated.py
  • Added a value to the VERSION enum to allow enabling the generated schema in configuration
• Adapt generated schema to be compatible with exporter code
  • Add alias functionality to VirtualField
  • When generating the schema, create aliases for columns in the stable spec that end in Key or Keys, as per Remove from field names ending "Key" and "Keys". Consistent singular and plural (for arrays) field names. poe-tool-dev/dat-schema#1
  • Add custom aliases for fields that have different names in the stable spec and the json schema
  • Open a pr to the schema repo adding fields only found in the python spec changes from wiki pypoe poe-tool-dev/dat-schema#60

Caveats

• The alpha and beta specs have been left as-is; it's not clear if they are used at all
• The name mapping heuristic for Key suffixes is completely naive; it only checks that a matching column exists in the target spec, not that the source and target columns have compatible types
• Similarly, the entire json schema could be validated against the stable spec, to notify us when a column is redefined, which may require a code change