Make fat-arrow handle both rest args and default values for parameters. Extract includes that users of macroes need to include as the macros expand to functions here (only for autocurry so far). Adds a bunch of tests; class, functions, destructuring, pipeline.
Remove rest.sjs macro, covered by 1-functions.sjs. Remove 1-default-args.sjs covered by 1-functions.sjs and 1-fat-arrow.sjs. Add back in the rest for rest args.