Bug 123406 Add geLocaltStringProperty in GroupElementHandle and GroupPropertyHandle
Please refer to 123405. GUI need a way to get the local setting of given property because current getStringPropery method will return inherited value if there are no local value.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/SimpleGroupElementHandle.java
* @see org.eclipse.birt.report.model.api.GroupElementHandle#getCommonProperties()
	 */
	public List getCommonProperties( )
	{
		List minProps = getMinPropDefns( );
		List commonProps = new ArrayList( minProps );
		Iterator iter = minProps.iterator( );
		while ( iter.hasNext( ) )
		{
			PropertyDefn propDefn = (PropertyDefn) iter.next( );
			for ( int i = 0; i < elements.size( ); i++ )
			{
				if ( !( (DesignElementHandle) elements.get( i ) ).getElement( )
						.getPropertyDefns( ).contains( propDefn ) )
				{
					commonProps.remove( propDefn );
					break;
				}
			}
		}
		return Collections.unmodifiableList(commonProps);
	}
	/**
	 * Returns the property definition list that has the minimum size.
	 * 
	 * @return the property definition list that has the minimum size.
	 */
	private List getMinPropDefns( )
	{
		int min = Integer.MAX_VALUE;