Bug 213126 Add support for DataEngine-leve dataset cache
In many cases the DataEngine-leve dataset cache is useful which ensure that a dataset is executed one time during rendering one report. To support this feature a new dataset property should be added. The Birt customer can choose whether this dataset need to be cached or not by setting the property in deisgn time.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/ModuleWriter.java
attribute( obj, DesignSchemaConstants.EXTENSION_NAME_ATTRIB,
					IExtendedItemModel.EXTENSION_NAME_PROP );
			attribute( obj, DesignSchemaConstants.EXTENSION_VERSION_ATTRIB,
					IExtendedItemModel.EXTENSION_VERSION_PROP );
			String name = (String) obj.getLocalProperty( getModule( ),
					IDesignElementModel.NAME_PROP );
			if ( !StringUtil.isBlank( name ) )
				writer.attribute( DesignSchemaConstants.NAME_ATTRIB, name );
			String extendsFrom = obj.getExtendsName( );
			if ( !StringUtil.isBlank( extendsFrom ) )
				writer.attribute( DesignSchemaConstants.EXTENDS_ATTRIB,
						extendsFrom );
			writer.attribute( DesignSchemaConstants.ID_ATTRIB, new Long( obj
					.getID( ) ).toString( ) );
			
			List props = extDefn.getProperties( );
			for ( int i = 0; i < props.size( ); i++ )
			{
				PropertyDefn prop = (PropertyDefn) props.get( i );
				String propName = prop.getName( );
				if ( IDesignElementModel.NAME_PROP.equals( propName )
						|| IExtendedItemModel.EXTENSION_NAME_PROP
								.equals( propName )
						|| IDesignElementModel.EXTENDS_PROP.equals( propName )
						|| IExtendedItemModel.EXTENSION_VERSION_PROP
								.equals( propName ) )
					continue;