Add screen mirroring, watch input, splash screen, and architecture docs

Mirrors the C64 text screen to the Pebble watch (with game-specific
  umlaut handling), adds a SELECT-triggered key wheel for sending
  navigation input back to the emulator, shows a splash screen on watch
  launch, and documents the resulting end-to-end architecture.

SchwertUndMagieOnPebbleWatchApp/package.json

@@ -24,10 +24,17 @@
     },
     "messageKeys": [
       "TIME",
-      "COMMAND"
+      "COMMAND",
+      "SCREEN"
     ],
     "resources": {
-      "media": []
+      "media": [
+        {
+          "type": "bitmap",
+          "name": "IMAGE_SPLASH",
+          "file": "splash.png"
+        }
+      ]
     }
   }
 }