Update SwapChain to configure texture usage

Explicitly configure swap chain usage in bindings and examples

Fix missing case in switch

Make swap chain Present usage implicit

Author: Austin Eng <enga@google.com>
diff --git a/examples/HelloTriangle.cpp b/examples/HelloTriangle.cpp
index 8d491f7..b9c9334 100644
--- a/examples/HelloTriangle.cpp
+++ b/examples/HelloTriangle.cpp
@@ -83,7 +83,7 @@
 
     queue = device.CreateQueueBuilder().GetResult();
     swapchain = GetSwapChain(device);
-    swapchain.Configure(nxt::TextureFormat::R8G8B8A8Unorm, 640, 480);
+    swapchain.Configure(nxt::TextureFormat::R8G8B8A8Unorm, nxt::TextureUsageBit::OutputAttachment, nxt::TextureUsageBit::OutputAttachment, 640, 480);
 
     initBuffers();
     initTextures();