- transform.py: syntax-tree traversal now passes not only the current node but the complete context (i.e. list of all parent nodes) to the transformation function.
- similarly parser.Compiler now stores the context (i.e. list of all parent nodes) in self.context.
- more documentation for parser.Compiler, parser.Parser and parser.Grammar

- syntaxtree.py: transformation_factory decorator for processing table functions; further type annotations

- syntaxtree.py: reversed parameter order in transformer-functions: node is now always the first paramter again.

- parser.py: bug: pos values not initialized in nodes in history record, in case root parser did not match