Started creating GuiEditKeyframe

Therefore, added support for floating point numbers in GuiNumberInput

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

@@ -1,9 +1,14 @@
 package eu.crushedpixel.replaymod.holders;
 
-public class Keyframe {
+public class Keyframe implements Cloneable {
 
     private final int realTimestamp;
 
+    @Override
+    public Object clone() {
+        return new Keyframe(realTimestamp);
+    }
+
     public Keyframe(int realTimestamp) {
         this.realTimestamp = realTimestamp;
     }