Fixes the 'assert on copy' bug.
Fixes the 'assert on copy' bug.

Some refactorings for easier reading.

Behvaioural changes:

- The isNullByDefault flag is propagated from children to it's parent,
if it is set to FALSE.

Alexpux/Coin3D,Alexpux/Coin3D,Alexpux/Coin3D,Alexpux/Coin3D