add token definitions from jls spec
tokens:  replace 'opt' with (?); knock binary literals into shape
tokens:  knock octal, decimal, and hex literals into shape
tokens cleanup:  surround character literals in quotes; two spaces of separation; | between alternatives; clean up InputElement
tokens: simplify, shorten, clarify, and factor in rules
get started on simple parser:  token, grammar definitions; tokenizer, etc.; many rules omitted for simplicity
continue simplest parser:  tokenizer; also fix up spec by simplifying decimal integer literal definition, and parsing nulls/booleans/keywords/identifiers together before later separating them