Bug 193245 Should block user to set content type property on the child element
After we switch from the slot to content element type property, all the rules that we applied to the slot before should be applied to the content element type property. When an element is extended from the library element, it should not be allowed to change the child element structure. So, when user call setProperty() to set the value of the content element type property, Model should throw out exception.
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/command/PropertyCommandTest.java
* <td>the value of structure was replaced</td>
 * </tr>
 * 
 * <tr>
 * <td></td>
 * <td>Undo the operation and use the first structure list in style2 to replace
 * the first structure list in My style</td>
 * <td>he value of structure was replaced</td>
 * </tr>
 * 
 * 
 * <tr>
 * <td>{@link #testRemoveAllItems()}</td>
 * <td>use propertycommand to remove all map-rule items</td>
 * <td>after remove all map-rule items ,the size of map.rules should be zero
 * </td>
 * </tr>
 * 
 * <tr>
 * <td>{@link #testInsertAndRemoveItem()}</td>
 * <td>insert new item named InsertAndRemove</td>
 * <td>after insert new item , size of rules changes to three</td>
 * </tr>
 * 
 * <tr>
 * <td></td>
 * <td>remove this new item</td>
 * <td>after remove that inserted item ,size of rules change to two</td>
 * </tr>
 *