Antlr-ast

- Fix get_cls in BaseNodeRegistry, now updates fields of classes already in the registry

- Support for Terminal nodes in `get_text`
- Add optional text attribute to BaseNode
- Fix marshalling to recursively transform children

- Return `None` if `get_position` has no better result
- Add type signatures
- Improve lexer errors

- Support `get_position` for Terminal nodes

- Rewrite as a staged approach
- autodetection of ANTLR fields and labels: Unshaped doesn’t exist anymore
- more isolated steps: enables serialization (and possibility to let ANTLR parser run in a separate service)
- more powerful definition of reshaped node (= AliasNode) fields using tree paths
- easier definition of transforms (simplification & AliasNodes) (no ANTLR API knowledge needed, no other visiting in transformation methods)
- more shared code

Added

- Add parameter to `parse` function to set a custom error listener (or remove the default listener)