Possible sollution for CC-16 (constructor injection)

- @configure annotated constructors must be public
- Inner classes are not supported as this requires Constretto to know the outer class instance. Trying to inject configuration on an inner class will throw a Constretto Exception.

Could posible be postphoned to future releases (e.g Constretto 2.1) as it does some fundamental classes (including the @Configure annotation). However the old Method injection logic is now used both for constructors and method and should be fairly stable