DERBY-6213: Deprecate support for Java 5 and CDC

- Make ColumnDescriptorList extend ArrayList<ColumnDescriptor> instead
  of ArrayList<TupleDescriptor>

- Make ConglomerateDescriptor extend ArrayList<ConglomerateDescriptor>
  instead of ArrayList<TupleDescriptor>

- Make GenericDescriptorList extend ArrayList<UniqueTupleDescriptor>
  instead of ArrayList<TupleDescriptor>

- Change signatures of getDescriptorViaIndex() and
  getDescriptorViaHeap() so that they can take lists of more specific
  types than List<TupleDescriptor>, and so that they can return a more
  specific type than TupleDescriptor

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1484821 13f79535-47bb-0310-9956-ffa450edef68