Bug 179931 Provide new interface IStyle to let extension return the style properties values
Provide the IStyle interface to let extension user can return the style property value list for their extension elements.
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/extension/PeerExtensionTest.java
ExtendedItemHandle extendedItem = (ExtendedItemHandle) designHandle
				.findElement( "testBox" ); 
		assertNotNull( extendedItem );
		
		assertEquals( IColorConstants.RED, extendedItem
				.getStringProperty( IStyleModel.COLOR_PROP ) );
		
		ExtendedItemHandle contentExtendedItem = (ExtendedItemHandle) designHandle
				.findElement( "headerMatrix" ); 
		assertEquals( IColorConstants.RED, contentExtendedItem
				.getStringProperty( IStyleModel.COLOR_PROP ) );
		
		
		TableHandle table = (TableHandle) designHandle
				.findElement( "testTable" ); 
		assertEquals( extendedItem, table.getContainer( ) );
		assertEquals( IColorConstants.RED, extendedItem
				.getStringProperty( IStyleModel.COLOR_PROP ) );
		
		assertEquals( DesignChoiceConstants.FONT_FAMILY_FANTASY, table
				.getStringProperty( IStyleModel.FONT_FAMILY_PROP ) );
		assertEquals( DesignChoiceConstants.FONT_SIZE_LARGER, table
				.getStringProperty( IStyleModel.FONT_SIZE_PROP ) );
		
		
		
		
		
		
		LabelHandle label = (LabelHandle) designHandle