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>Property is set successfully.</td>
 * </tr>
 * 
 * <tr>
 * <td></td>
 * <td>The name can be found in the meta.xml and the property is an intrinsic
 * property</td>
 * <td>property value is set successfully.</td>
 * </tr>
 * 
 * <tr>
 * <td></td>
 * <td>Changes property value and checks property value.</td>
 * <td>getProperty is the same as input value</td>
 * </tr>
 * 
 * <tr>
 * <td>{@link #testSetandClearProperty()}</td>
 * <td>set property value and check the get property value</td>
 * <td>the value of property is the same as input value</td>
 * </tr>
 * 
 * <tr>
 * <td></td>
 * <td>clear property value and check the result</td>
 * <td>after clear property , the size of result is zero.</td>
 * </tr>
 * 
 * <tr>
 * <td>{@link #testAddItem()}</td>