Support Lazy Attribute Population

[Ichimonji10]

Make Entity objects support lazy attribute population.

The following code is currently valid:

Product(id=5).read().id
Product(id=5).read().name
Product(id=5).read().organization.id

The following code is currently invalid but should be valid:

Product(id=5).read().organization.name
Repository(id=10).read().product.organization.id
Repository(id=10).read().product.organization.name