Added Event Markers to Replay, which allow players to quickly mark important events while recording (M key by default)

Added Event Marker Indicators to be displayed on GuiTimeline

src/main/java/eu/crushedpixel/replaymod/holders/Marker.java

@@ -0,0 +1,45 @@
+package eu.crushedpixel.replaymod.holders;
+
+import org.apache.commons.lang3.builder.HashCodeBuilder;
+
+public class Marker {
+
+    public Marker(Position position, int timestamp, String name) {
+        this.position = position;
+        this.timestamp = timestamp;
+        this.name = name;
+    }
+
+    private Position position;
+    private int timestamp;
+    private String name;
+
+    public Position getPosition() {
+        return position;
+    }
+
+    public int getTimestamp() {
+        return timestamp;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public boolean equals(Object o2) {
+        if(o2 == null) return false;
+        if(!(o2 instanceof Marker)) return false;
+        Marker m2 = (Marker)o2;
+        return hashCode() == m2.hashCode();
+    }
+
+    @Override
+    public int hashCode() {
+        return new HashCodeBuilder(17, 37)
+                .append(position)
+                .append(timestamp)
+                .append(name)
+                .toHashCode();
+    }
+}