Implicit field accessors

[rymiel]

yume/example/struct.ym

Lines 3 to 4 in 1dcc8e2

	# TODO
	# These field accessors will be implicitly defined one day

Unless the user has defined their own getter/setter for a specific field, or the field is marked private (also not implemented); Implicit accessors should be defined for each field.

More generally, there's other stuff that should also be "implicit", but aren't at all, such as constructors (i.e. default constructor)