ParserLog: Finished the AST pretty-printer.
ParserMain: The CLI "ast" is now "ast-tokens" and the new "ast"
calls the AST pretty-printer.
Bug: Added nat literals as patterns.
AST: Removed unary constructor TupleInj.
Parser and simplifier:
- The rule "cartesian" is now properly stratified.
- Parenthesised expressions now correctly create EPar nodes.