Move all engine stuff to GoRetro. Still many interactions between game and engine code that there should not be.

goretro.go

@@ -0,0 +1,17 @@
+package GoRetro
+
+import "time"
+
+const (
+	ScreenWidth  = 1024
+	ScreenHeight = 768
+
+	TargetTicksPerSecond   = 60
+	DebugStatePrintSeconds = 1
+
+	dataDir = "data/"
+)
+
+var Delta float64
+var LastDebugStatePrint time.Time
+var DebugTick bool