Most files suffered major changes

- Less ambiguous syntax
- Better parser (Chumsky only does tokenization now)
- Tidy(|ier) error handling
- Facade for simplified embedding
- External code grouped in (fairly) self-contained Systems
- Dynamic action dispatch
- Many STL additions

src/interpreter/mod.rs

@@ -2,8 +2,10 @@
 mod apply;
 mod context;
 mod error;
+mod handler;
 mod run;
 
 pub use context::{Context, Return};
 pub use error::RuntimeError;
-pub use run::{run, run_handler, Handler, HandlerErr, HandlerParm, HandlerRes};
+pub use handler::{run_handler, HandlerRes, HandlerTable};
+pub use run::run;