Updated metadata files

SceneKitViewer/Metadata.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <SampleMetadata>
   <ID>FFD5B679-BF48-402A-AD8E-02DE48730E3D</ID>
+  <Brief>This is a Xamarin.Mac version of Apple's simple SceneKitViewer.</Brief>
   <IsFullApplication>true</IsFullApplication>
   <Level>Intermediate</Level>
   <Tags>Games, SceneKit</Tags>

yosemite/Bananas/Metadata.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <SampleMetadata>
 	<ID>3986c99a-7682-45b6-a59c-8faf566593cd</ID>
+	<Brief>This sample shows how to build a basic game using Scene Kit.</Brief>
 	<IsFullApplication>true</IsFullApplication>
 	<Level>Advanced</Level>
 	<Tags>Games, Graphics, SceneKit, Yosemite</Tags>

yosemite/SceneKitSessionWWDC2013/Metadata.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <SampleMetadata>
   <ID>9126871f-afe5-4837-ae18-cb7966da4ad6</ID>
+  <Brief>This application render a 3D environment and presents a series of slides with Scene Kit objects.</Brief>
   <IsFullApplication>true</IsFullApplication>
   <Level>Intermediate</Level>
   <Tags>Games, Graphics, SceneKit, Yosemite</Tags>

yosemite/SceneKitSessionWWDC2014/Metadata.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <SampleMetadata>
   <ID>3b3889a9-ffa2-4bae-9c68-a340cfa294ac</ID>
+  <Brief>This application render a 3D environment and presents a series of slides with Scene Kit objects.</Brief>
   <IsFullApplication>true</IsFullApplication>
   <Level>Intermediate</Level>
   <Tags>Games, Graphics, SceneKit, Yosemite</Tags>