Bug 164070 Support widows/orphans properties on text item
Support widows/orphans properties on block text item(label, text, data etc), About the definition of widows/orphans, please refer to CSS spec.
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/api/DesignElementHandleTest.java
* <td>the return slot handle is null</td>
 * </tr>
 * <tr>
 * <td>testStyle()</td>
 * <td>Gets private and shared style from a label with a shared style.</td>
 * <td>The label has both private and shared styles.</td>
 * </tr>
 * <tr>
 * <td></td>
 * <td>Gets private and shared style from a label without a shared style and no
 * private style defined on it.</td>
 * <td>The label has the private style.</td>
 * </tr>
 * <tr>
 * <td></td>
 * <td>Gets private and shared style from a label without a shared style but
 * with a private style.</td>
 * <td>The label only has the private style.</td>
 * </tr>
 * <tr>
 * <td></td>
 * <td>Sets and clears the style on the label.</td>
 * <td>The style is set correctly.</td>
 * </tr>
 * <tr>
 * <td></td>
 * <td>Sets the style on the label with another element.</td>
 * <td>Throws <code>StyleException</code> with an error code
 * <code>NOT_FOUND</code>.</td>
 * </tr>