Fix docblocks and minor refactoring of __get() method

Type `Table` doesn't necessarily mean object of class `Cake\ORM\Table`. Using `ModelAwareTrait::modelFactory()` you can configure a callable for type `Table` which can return an instance of any class.

Though it would be would be wacky to use type name `Table` if not using class `Cake\ORM\Table` or a class which extends it.