Added grammar support for expression level message chaining by using ;
which reduces the need for parenthesises in certain situations.

E.g.

1.to: 100; map: {\x * \x}; where: {\x.isEven}; each: {writeln: \x}

rather than

(((1.to: 100) map: {\x * \x}) where: {\x.isEven}) each: {writeln: \x}

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>