Add `ManyToMany.has()` and `ManyToMany.toList()`, and fix other methods.
Add `ManyToMany.has()` and `ManyToMany.toList()`, and fix other methods.

Previously several methods only referenced bList, and ignored unsavedBObjects.
Now they use the new toList() first.

Also added documentation for each of these methods.

ufront/ufront-orm