Adds let statements.
Adds return statements.
Adds stub while statement and partially done if statement.
Fixup, allows multiple statements in an if.
Adds while statement.
Adds else statements to if.
Adds type.
Fixup of type breaking if feed an empty list.
Adds parameters and parameter lists.
Adds partial classVarDec.
Adds partial varDec.
Adds subroutine body.
Adds subroutine body.
Refactors to use literal consumer everywhere.
Adds class consumer.
Fixes typo and missing semi colon.
Literal consumer will no longer break if tokens in empty.
Fixes expression to be able to start with a unary op.
Fixes return statements to make the expression optional.
Fixup typo of null.