Add FrequencySetting for group in Marshalling test

eraser-base/src/main/jastadd/Printing.jrag

@@ -121,6 +121,7 @@ aspect Printing {
         .addIds("groups", getNumGroup(), getGroups())
         .addIds("items", getNumItem(), getItems())
         .addOptionalPrettyPrint(getAggregationFunction())
+        .addOptional("performance", hasFrequencySetting(), () -> getFrequencySetting().getID())
         .build();
   }
 

eraser-base/src/test/resources/tests/ppc2/input.eraser

 Mqtt: incoming="ppc2/" outgoing="oh2/in" host="localhost" ;
 Item: id="iris1_item" label="Iris 1" state="121,88,68" topic="iris1_item/state" performance="ip1" ;
-Group: id="my-group" items=["iris1_item"] ;
+Group: id="my-group" items=["iris1_item"] performance="ip1" ;
 ThingType: id="skywriter-hat" label="SkyWriterHAT" description="SkyWriterHAT Gesture Recognition" parameters=["brokername"] channelTypes=["flick-type"] ;
 ChannelType: id="flick-type" itemType="String" label="Last Flick" description="Last Flick detected (and its direction)" category="Motion" readOnly ;
 Parameter: id="brokername" type="text" required label="Broker Name" description="Name of the broker as defined in the <broker>.url in services/mqtt.cfg. See the MQTT Binding for more information on how to configure MQTT broker connections." context="service" default="mosquitto" ;

eraser-base/src/test/resources/tests/ppc2/output.eraser

 Item: id="iris1_item" label="Iris 1" state="121,88,68" topic="iris1_item/state" performance="ip1" ;
-Group: id="my-group" items=["iris1_item"] ;
+Group: id="my-group" items=["iris1_item"] performance="ip1" ;
 ThingType: id="skywriter-hat" label="SkyWriterHAT" description="SkyWriterHAT Gesture Recognition" parameters=["brokername"] channelTypes=["flick-type"] ;
 ChannelType: id="flick-type" label="Last Flick" description="Last Flick detected (and its direction)" itemType="String" category="Motion" readOnly ;
 Parameter: id="brokername" label="Broker Name" description="Name of the broker as defined in the <broker>.url in services/mqtt.cfg. See the MQTT Binding for more information on how to configure MQTT broker connections." type="Text" context="service" default="mosquitto" required ;