Unify the code in parent node implementations.

git-svn-id: https://svn.apache.org/repos/asf/webservices/axiom/trunk@1608309 13f79535-47bb-0310-9956-ffa450edef68
Drop the requirement to override every superclass method in OMSourcedElementImpl. This is simply not scalable and it prevents us from declaring methods final where appropriate (as required by good design).

git-svn-id: https://svn.apache.org/repos/asf/webservices/axiom/trunk@1608310 13f79535-47bb-0310-9956-ffa450edef68
CoreChildNode should not extend OM interfaces.

git-svn-id: https://svn.apache.org/repos/asf/webservices/axiom/trunk@1608312 13f79535-47bb-0310-9956-ffa450edef68