Added grammar support for dict-from-context. #[] dicts are implicitly
derived from Any unconditionally. #{} are implicitly derived from a
contextual dict.

E.g.

// Derived from any
O = #{
}

I = #[
	SHARED // "Class fields" - not used (below) in "instances"/derivations
	x y z // "Instance fields" - declared to be part of the lexical context
	// Derived from I; x y z are part of the derivation
	new => |anX aY aZ| #{
		x = anX
		y = aY
		z = aZ
	}
	m => x * y * z
]

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