[DRAFT] schema to python package

• Code is a copy of Pymemri schema, it will removed from there and imported here
• Schema is now defined in python, in memri_schema/schema_definitions.py . No changes to definitions compared to dev
• schema versioning in init.py
• json export in /tools, added a test to see if the export in generated/schema.json matches the schema.
• can also do the export + commit in CI, doesnt seem like high priority.
• Moving the pymemri tests that are not dependent on Pod to here (TODO)
• keeping integration tests with Pod in pymemri for now