Add common pathing code and SimplePathing module

src/main/java/com/replaymod/pathing/player/RealtimeTimelinePlayer.java

@@ -0,0 +1,52 @@
+package com.replaymod.pathing.player;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import com.replaymod.pathing.path.Timeline;
+import com.replaymod.replay.ReplayHandler;
+import net.minecraftforge.fml.common.gameevent.TickEvent;
+
+/**
+ * Timeline player using the system time.
+ */
+public class RealtimeTimelinePlayer extends AbstractTimelinePlayer {
+    /**
+     * Wether the next frame is the first frame.
+     * We only start measuring time from the second frame
+     * as the first might have to jump in time which might take time.
+     */
+    private boolean firstFrame;
+    private boolean secondFrame;
+
+    /**
+     * System time in milliseconds at the start.
+     */
+    private long startTime;
+
+    public RealtimeTimelinePlayer(ReplayHandler replayHandler) {
+        super(replayHandler);
+    }
+
+    @Override
+    public ListenableFuture<Void> start(Timeline timeline) {
+        firstFrame = true;
+        return super.start(timeline);
+    }
+
+    @Override
+    public void onTick(TickEvent.RenderTickEvent event) {
+        if (secondFrame) {
+            secondFrame = false;
+            startTime = System.currentTimeMillis();
+        }
+        super.onTick(event);
+        if (firstFrame) {
+            firstFrame = false;
+            secondFrame = true;
+        }
+    }
+
+    @Override
+    public long getTimePassed() {
+        return firstFrame ? 0 : System.currentTimeMillis() - startTime;
+    }
+}