Static inner classes can be manipulated by javassist

The static inner classes can be manipulated, but the non static inner classes can't (limitation of javassist documented in the plugin code).

This commit allows ClassTransformers to transform all inner classes, I think the javassist APIs don't allow to check wether a class is an inner class or not, and neither to check if an inner class is static or not.

Nevertheless, I needed to be able to transform static inner classes and I achieved to do it with the plugin thanks to this change.

Would you accept the PR ?