Warning, GIGANTIC COMMIT!

Replaced Keyframe subclasses with Generic Types of Keyframe and replaced all instanceof calls
Replaced implementations of Linear and Spline interpolation to interpolate any Object that extends KeyframeValue and contains at least one public double Field. I'll need this for Keyframe interpolation in CustomImageObject Transformations
Made MarkerKeyframe *no* subclass of Keyframe to avoid conflicts with PositionKeyframe in instanceof checks for Keyframe#getValue
Created KeyframeList which extends ArrayList to provide some helping functions which DRY up the ReplayHandler
Split up ReplayHandler's keyframeList into timeKeyframeList and positionKeyframeList

src/main/java/eu/crushedpixel/replaymod/interpolation/GenericLinearInterpolation.java

@@ -0,0 +1,60 @@
+package eu.crushedpixel.replaymod.interpolation;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.List;
+
+public class GenericLinearInterpolation<T extends KeyframeValue> implements Interpolation<T> {
+
+    private Field[] fields;
+
+    protected List<T> points = new ArrayList<T>();
+
+    public GenericLinearInterpolation() {
+        points = new ArrayList<T>();
+    }
+
+    @Override
+    public void prepare() {}
+
+    public void addPoint(T point) {
+        points.add(point);
+
+        List<Field> fields = new ArrayList<Field>();
+        for(Field f : point.getClass().getDeclaredFields()) {
+            if(Modifier.isPublic(f.getModifiers())) {
+                fields.add(f);
+            }
+        }
+        this.fields = fields.toArray(new Field[fields.size()]);
+    }
+
+    @Override
+    public void applyPoint(float position, T toEdit) {
+        if(points.isEmpty()) {
+            throw new IllegalStateException("At least one Value needs to be added for this operation");
+        }
+
+        //first, get previous and next T for given position
+        float relative = position * (points.size()-1);
+        int previousIndex = (int)Math.floor(relative);
+        int nextIndex = (int)Math.ceil(relative);
+        float percentage = relative - previousIndex;
+
+        T previous = points.get(previousIndex);
+        T next = points.get(nextIndex);
+
+        for(Field f : fields) {
+            try {
+                f.set(toEdit, getInterpolatedValue(f.getDouble(previous), f.getDouble(next), percentage));
+            } catch(Exception e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    private double getInterpolatedValue(double val1, double val2, float perc) {
+        return val1 + ((val2 - val1) * perc);
+    }
+}