titlescreen moved to modules; using GLES 3.0 as default

src/net/torvald/terrarum/ModuleEntryPoint.kt

@@ -1,9 +1,12 @@
 package net.torvald.terrarum
 
+import com.badlogic.gdx.graphics.g2d.SpriteBatch
+
 /**
  * Created by minjaesong on 2018-06-21.
  */
 abstract class ModuleEntryPoint {
     abstract fun invoke()
     abstract fun dispose()
+    open fun getTitleScreen(batch: SpriteBatch): IngameInstance? = null
 }